Access control method and apparatus for use in mobile communication

ABSTRACT

The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on 5G communication technology and IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A handover method of a terminal in a mobile communication system according to the present disclosure includes transmitting UE capability information including a random access-free handover indicator to a first base station, receiving a handover command message from the first base station, and transmitting, when the handover command message includes uplink resource information, a handover complete message to a second base station based on the uplink resource information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/453,867 filed on Jun. 26, 2019, which is a continuation of U.S.patent application Ser. No. 15/649,558 filed on Jul. 13, 2017, now U.S.Pat. No. 10,349,318 issued on Jul. 9, 2019, which is based on and claimspriority to Korean Patent Application No. 10-2016-0088758 filed on Jul.13, 2016, the disclosures of which are herein incorporated by referencein their entirety.

BACKGROUND 1. Field

The present disclosure relates to a mobile communication system and, inparticular, to a method for determining whether to bar an access in amobile communication system.

Also, the present disclosure relates to a method for configuringDiscontinuous Reception (DRX) in a mobile communication system.

Also, the present disclosure relates to a method for transmitting apaging signal to a terminal in a mobile communication system.

Also, the present disclosure relates to a data transmission andreception method for Ultra-Reliable and Low-Latency Communication(URLLC) service in a mobile communication system.

Also, the present disclosure relates to a method for reducing datainterruption time during a handover procedure and handling failure ofdata interruption time reduction in a mobile communication system.

Also, the preset disclosure relates to a method and apparatus for aterminal to switch autonomously to a large paging area preference modeand updating the paging area in a mobile communication system.

Also, the present disclosure relates to a paging message-based modetransition method and apparatus of a terminal for use in a mobilecommunication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), Full Dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud Radio Access Networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,Coordinated Multi-Points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”.“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology. Meanwhile, an LTEsystem may determine whether to perform application-specific accessbarring and control accesses per application. However, the complicatingapplication-specific access barring mechanism gives rise to thenecessity of a consistent access control mechanism.

Meanwhile, with two DRX cycles (long DRX cycle and short DRX cycle)specified in LTE standard, it may be impossible to adjust the DRX cycledynamically according to Data Radio Bearer (DRB) characteristics,traffic pattern, and buffer status. Thus, there is a need of a methodfor adjusting the length of the DRX cycle efficiently.

In LTE, a new operation mode, called light connection mode, has beenproposed to define a state where a base station (evolved Node B: eNB)and a terminal (User Equipment: UE) maintain the UE information (e.g.,context information) even when the connection therebetween isdisconnected in addition to the idle mode and the connected mode. In anLTE system, if the tracking area of a UE in the light connection mode ischanged, the UE may transition to the connected mode and transmit atracking area update message to the core network. This means that the UEhas to transition to the connected mode despite no data to transmit.

For next generation mobile communication systems, it may be consideredto use Ultra Reliable (packet error rate of 10-5) Low-LatencyCommunication (URLLC) services. Examples of the URLLC services mayinclude an automated vehicle service, an e-health service, and a droneservice. In the LTE system, the negative acknowledgement (NACK)corresponding to a packet transmission trigger retransmission and thusmay cause transmission latency. There is therefore a need of specifyingdetailed operation for retransmitting URLLC service packets efficiently.

In a case where a UE is handed from one eNB to another in the LTEsystem, the UE cannot communicate data with the network during a periodbetween the time point when it receives a handover command message fromthe source eNB and the time point when the UE transmits a handovercomplete message to the target eNB. Here, the period during which datatransmission is impossible is called data interruption time. Typically,the data interruption time lasts at least a few dozen milliseconds (ms),resulting in data cutoff. Thus, there is a need of a method forminimizing the data interruption time.

In a network supporting the light connection mode, the UE in the idlemode may report UE location on the move in the paging area configured bythe network. In this case, a large amount of signaling is requiredbetween the UE and the eNB in order for the UE to transition to a largepaging area preference mode for battery power saving.

Also, in the case that the UE stays in the light connected mode foralong time, the network has to store and maintain the UE context andS1-U bearer information. This means that the network cannot manage theUEs in the light connected mode continuously but controls them totransition to the RRC Idle mode. This operation for transitioning the UEoperation mode from the light connected mode to the RRC Idle mode maycause significant signaling overhead.

SUMMARY

To address the above-discussed deficiencies, it is a primary object toprovide a method and apparatus for adopting a consistent access controlmechanism.

Also, the present disclosure aims to provide a method and apparatus forchanging the DRX cycle dynamically according to DRB characteristics,traffic pattern, and buffer status.

Also, the present disclosure aims to provide a method and apparatus forpaging UEs within a cell in a heterogeneous network environment with theeNBs having different cell sizes.

Also, the present disclosure aims to provide a datatransmission/reception method and apparatus for URLLC service.

Also, the present disclosure aims to provide a method and apparatus forreducing the data interruption time during the handover of a UE andhandling failure data interruption time reduction.

Also, the present disclosure aims to provide an operation modetransition method and apparatus of a UE for transitioning to a largepaging area preference mode autonomously to reduce signaling overhead.

Furthermore, the present disclosure aims to provide a pagingmessage-based operation mode transition method and apparatus of a UE forreducing signaling overhead.

In accordance with an aspect of the present disclosure, a method of auser equipment (UE) in a mobile communication system, the methodcomprising transmitting UE capability information including a randomaccess-free handover indicator to a first base station, receiving ahandover command message from the first base station, and transmitting,if the handover command message includes uplink resource information, ahandover complete message to a second base station based on the uplinkresource information.

In accordance with another aspect of the present disclosure, a method ofa first base station in a mobile communication system, the methodcomprising receiving user equipment (UE) capability informationincluding a random access-free handover indicator from a UE,transmitting a handover request message to a second base station,receiving a handover request acknowledgement (ACK) message, andtransmitting, if the handover request ACK message includes uplinkresource information, a handover command message including the uplinkresource information to the UE, wherein the uplink resource informationis used for transmission of a handover complete message from the UE tothe second base station.

In accordance with another aspect of the present disclosure, a method ofa second base station in a mobile communication system, the methodcomprising receiving a handover request message from a first basestation, transmitting a handover request acknowledgement (ACK) message,and receiving, if the handover request ACK message includes uplinkresource information, a handover complete message from a user equipment(UE) based on the uplink resource information.

In accordance with another aspect of the present disclosure, a userequipment (UE) in a mobile communication system, the UE comprising atransceiver configured to transmit or receive signals and a controllerconfigured to transmit user equipment (UE) capability informationincluding a random access-free handover indicator to a first basestation, receive a handover command message from the first base station,and transmit, if the handover command message includes uplink resourceinformation, a handover complete message to a second base station basedon the uplink resource information.

In accordance with another aspect of the present disclosure, a firstbase station in a mobile communication system, the first base stationcomprising a transceiver configured to transit or receive signals; and acontroller configured to receive user equipment (UE) capabilityinformation including a random access-free handover indicator from a UE,transmit a handover request message to a second base station, receive ahandover request acknowledgement (ACK) message from the second basestation, and transmit, if the handover request ACK message includesuplink resource information, a handover command message including theuplink resource information to the UE, the uplink resource informationbeing used for transmission of a handover complete message from the UEto the second base station.

In accordance with still another aspect of the present disclosure, asecond base station in a mobile communication system, the second basestation comprising a transceiver configured to transit or receivesignals; and a controller configured to receive a handover requestmessage from a first base station, transmit a handover requestacknowledgement (ACK) message, and receive, if the handover request ACKmessage includes uplink resource information, a handover completemessage from a user equipment (UE) based on the uplink resourceinformation.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or, the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1A illustrates an architecture of an LTE system to which thepresent disclosure is applied;

FIG. 1B illustrates an access barring determination method in an LTEsystem;

FIG. 1C illustrates an ACDC procedure in an LTE system;

FIG. 1D illustrates a structure of ACDC configuration information forsue in an LTE system;

FIG. 1E illustrates an access barring determination method of thepresent disclosure;

FIG. 1F illustrates a structure of access barring configurationinformation according to the present disclosure;

FIG. 1G illustrates an access barring determination method according tothe present disclosure;

FIG. 1H illustrates UE operations according to the present disclosure;

FIG. 1I illustrates an access barring determination method of a UEaccording to the present disclosure;

FIG. 1J illustrates a configuration of a UE of the present disclosure;

FIG. 1K illustrates a configuration of an eNB of the present disclosure;

FIG. 2A illustrates an LTE architecture;

FIG. 2B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system;

FIG. 2C illustrates a DRX operation;

FIG. 2D illustrates the concept of a DRX operation in the connected modeaccording to the present disclosure;

FIG. 2E illustrates signal flows in a DRX procedure for a UE accordingto the present disclosure;

FIG. 2FA illustrates a DRX operation of a UE according to the presentdisclosure;

FIG. 2FB illustrates a DRX operation of an eNB according to the presentdisclosure;

FIG. 2G illustrates MAC CE formats according to the present disclosure;

FIG. 2H illustrates a best beam pair according to the presentdisclosure;

FIG. 2I illustrates a DRX operation in the beam measurement resultreport process according to the present disclosure;

FIG. 2J illustrates a beam measurement result report procedure accordingto the present disclosure;

FIG. 2KA illustrates UE operations in the beam measurement result reportprocedure according to the present disclosure;

FIG. 2KB illustrates eNB operations in the beam measurement resultreport procedure according to the present disclosure;

FIG. 2L illustrates a configuration of a UE according to the presentdisclosure;

FIG. 2M illustrates a configuration of an eNB according to the presentdisclosure;

FIG. 3A illustrates an LTE system architecture;

FIG. 3B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system;

FIG. 3C illustrates a network environment to which the presentdisclosure is applied;

FIG. 3D illustrates a proposed paging procedure between a terminal and anetwork according to the present disclosure;

FIG. 3E illustrates a paging area update procedure of a terminalaccording to the present disclosure;

FIG. 3F illustrates a configuration of a terminal according to thepresent disclosure;

FIG. 4A illustrates an LTE system architecture;

FIG. 4B illustrates a protocol stack of an interface between a terminaland an eNB in the LTE system;

FIG. 4C illustrates signal flows between a terminal and a base stationin a signal transmission method proposed in the present disclosure;

FIG. 4DA illustrates a transmission scheme proposed in the presentdisclosure;

FIG. 4DB illustrates another transmission scheme proposed in the presentdisclosure;

FIG. 4DC illustrates another transmission scheme proposed in the presentdisclosure;

FIG. 4EA illustrates a terminal operation according to the presentdisclosure;

FIG. 4EB illustrates a base station operation according to the presentdisclosure:

FIG. 4F illustrates a configuration of a terminal according to anembodiment of the present disclosure;

FIG. 4G illustrates a configuration of a base station according to anembodiment of the present disclosure;

FIG. 5A illustrates an LTE system architecture;

FIG. 5B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system;

FIG. 5C illustrates a handover procedure in a legacy LTE system;

FIG. 5D illustrates a RACH-less handover method proposed in the presentdisclosure;

FIG. 5E illustrates another RACH-less handover method proposed in thepresent disclosure;

FIG. 5F illustrates a RACH-less handover procedure for reducing datatransmission suspension time by configuring a UE-initiated timer (Timer1) especially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason;

FIG. 5G is illustrates another RACH-less handover procedure for reducingdata transmission suspension time by configuring a UE-initiated timerespecially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason;

FIG. 5H illustrates a RACH-less handover procedure for reducing datatransmission suspension time by configuring a network-initiated timer(Timer 2) especially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason;

FIG. 5I illustrates another RACH-less handover procedure for reducingdata transmission suspension time by configuring a network-initiatedtimer (Timer 2) especially when a UE cannot be allocated uplinkresources for transmission to a target eNB for any reason;

FIG. 5I illustrates a UE operation according to the present disclosure;

FIG. 5K illustrates another UE operation according to the presentdisclosure;

FIG. 5L illustrates another UE operation according to the presentdisclosure;

FIG. 5M illustrates a configuration of a UE according to an embodimentof the present disclosure;

FIG. 5N illustrates a configuration of an eNB including a mobilitymanagement entity (MME) part and a S-GW part according to an embodimentof the present disclosure;

FIG. 6A illustrates an LTE system architecture;

FIG. 6B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system.

FIG. 6C illustrates the concept of light connection;

FIGS. 6DA and 6DB illustrate signal flows among a UE, an anchor eNB, anew eNB, and an MME for UE context and S1 bearer reuse in lightconnection procedure according to the present disclosure;

FIG. 6E illustrates a PA update procedure for a UE in a networksupporting a light connection technique according to the presentdisclosure;

FIG. 6F illustrates diverse types of PA according to the presentdisclosure;

FIG. 6G illustrates signal flows between a UE and eNBs in a PAreconfiguration procedure according to the present disclosure;

FIG. 6H illustrates another procedure for PA reconfiguration for a UEaccording to the present disclosure;

FIG. 6I illustrates an autonomous PA reconfiguration procedure of a UEaccording to the present disclosure;

FIG. 6J illustrates a configuration of a UE according to an embodimentof the present disclosure;

FIG. 6K illustrates a configuration of an eNB including an MME part andan S-GW part according to an embodiment of the present disclosure;

FIG. 7A illustrates an LTE system architecture;

FIG. 7B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system;

FIG. 7C illustrates the concept of light connection;

FIGS. 7DA and 7DB illustrate signal flows among a UE, an anchor eNB, anew eNB, and an MME for UE context and S1 bearer reuse in lightconnection procedure according to the present disclosure;

FIG. 7E illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode according to the present disclosure;

FIG. 7F illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode, when the UE moves to a PA ofanother eNB, according to the present disclosure;

FIG. 7G illustrates another procedure for transitioning a UE in thelight connected mode to the RRC idle mode according to the presentdisclosure;

FIG. 7H illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode using a paging message including anRRC idle mode transition indicator:

FIG. 7I illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode using a paging message including anRRC idle mode transition indicator, when the UE moves to a PA of anothereNB, according to the present disclosure;

FIG. 7J illustrates another procedure for transitioning a UE in thelight connected mode to the RRC idle mode according to the presentdisclosure;

FIG. 7K illustrates a UE operation, when a paging message is received,according to the present disclosure;

FIG. 7L illustrates a configuration of a UE according to an embodimentof the present disclosure; and

FIG. 7M illustrates a configuration of an eNB including an MME part andan S-GW part according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1A through 7M, discussed below, and the various embodiments usedto describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Although the description is mainly directed to Long-Term Evolution (LTE)and Evolved Packet Core (EPC) for Radio Access Network (RAN) and CoreNetwork (CN) that are standardized by the 3rd Generation PartnershipProject (3GPP), it will be understood by those skilled in the art thatthe present disclosure can be applied even to othercommunication/computing systems having the similar technical backgroundand channel format, with a slight modification, without departing fromthe spirit and scope of the present disclosure.

Detailed description of well-known functions and structures incorporatedherein may be omitted to avoid obscuring the subject matter of thepresent disclosure. This aims to omit unnecessary description so as tomake the subject matter of the present disclosure clear.

For the same reason, some elements are exaggerated, omitted, orsimplified in the drawings and, in practice, the elements may have sizesand/or shapes different from those shown in the drawings. The samereference numbers are used throughout the drawings to refer to the sameor like parts.

It is to be appreciated that those skilled in the art can change ormodify the embodiments without departing the technical concept of thisdisclosure. Accordingly, it should be understood that above-describedembodiments are essentially for illustrative purpose only but not in anyway for restriction thereto.

In the above described embodiments of the present disclosure, the stepsand message transmissions may become the targets of being selectivelycarried out or omitted. In each embodiment of the present disclosure,the operations are not necessary to be performed in the sequential orderas depicted but may be performed in a changed order. Each step andmessage may be performed independently.

Some or all of the tables exemplified in the above-description areprovided to help understand the present disclosure. Accordingly, thedetailed description of the table is to express part of the method andapparatus proposed in the present disclosure. That is, it is preferredto approach the content of the table of the specification semanticallyrather than syntactically. Although various embodiments of the presentdisclosure have been described using specific terms, the specificationand drawings are to be regarded in an illustrative rather than arestrictive sense in order to help understand the present disclosure. Itis obvious to those skilled in the art that various modifications andchanges can be made thereto without departing from the broader spiritand scope of the disclosure.

Advantages and features of the present disclosure and methods ofaccomplishing the same may be understood more readily by reference tothe following detailed description of exemplary embodiments and theaccompanying drawings. The present disclosure may, however, be embodiedin many different forms and should not be construed as being limited tothe exemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the concept of the disclosure to thoseskilled in the art, and the present disclosure will only be defined bythe appended claims. Like reference numerals refer to like elementsthroughout the specification.

It will be understood that each block of the flowcharts and/or blockdiagrams, and combinations of blocks in the flowcharts and/or blockdiagrams, can be implemented by computer program instructions. Thesecomputer program instructions may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable data processing apparatus, such that the instructions whichare executed via the processor of the computer or other programmabledata processing apparatus create means for implementing thefunctions/acts specified in the flowcharts and/or block diagrams. Thesecomputer program instructions may also be stored in a non-transitorycomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the non-transitorycomputer-readable memory produce manufacture articles embeddinginstruction means which implement the function/act specified in theflowcharts and/or block diagrams. The computer program instructions mayalso be loaded onto a computer or other programmable data processingapparatus to cause a series of operational steps to be performed on thecomputer or other programmable apparatus to produce a computerimplemented process such that the instructions which are executed on thecomputer or other programmable apparatus provide steps for implementingthe functions/acts specified in the flowcharts and/or block diagrams.

Furthermore, the respective block diagrams may illustrate parts ofmodules, segments, or codes including at least one or more executableinstructions for performing specific logic function(s). Moreover, itshould be noted that the functions of the blocks may be performed in adifferent order in several modifications. For example, two successiveblocks may be performed substantially at the same time, or may beperformed in reverse order according to their functions.

According to various embodiments of the present disclosure, the term“module”, means, but is not limited to, a software or hardwarecomponent, such as a Field Programmable Gate Array (FPGA) or ApplicationSpecific Integrated Circuit (ASIC), which performs certain tasks. Amodule may advantageously be configured to reside on the addressablestorage medium and configured to be executed on one or more processors.Thus, a module may include, by way of example, components, such assoftware components, object-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. The functionality provided for in the components andmodules may be combined into fewer components and modules or furtherseparated into additional components and modules. In addition, thecomponents and modules may be implemented such that they execute one ormore CPUs in a device or a secure multimedia card.

First Embodiment

Detailed description of well-known functions and structures incorporatedherein may be omitted to avoid obscuring the subject matter of thepresent disclosure. Exemplary embodiments of the present disclosure aredescribed with reference to the accompanying drawings in detail.

FIG. 1A illustrates an LTE system to which the present disclosure isapplied.

In reference to FIG. 1A, the Radio Access Network (RAN) of the LTEsystem includes evolved Node Bs (eNBs) 1 a-05, 1 a-10, 1 a-15, and 1a-20; a Mobility Management Entity (MME) 1 a-25; and a Serving Gateway(S-GW) 1 a-30. The User Equipment (UE) 1 a-35 connects to an externalnetwork via the eNBs 1 a-05, 1 a-10, 1 a-15, and 1 a-20 and the S-GW 1a-30.

The eNBs 1 a-05, 1 a-10, 1 a-15, and 1 a-20 are equivalent to the legacynode Bs of the universal mobile telecommunications system (UMTS).

The UE 1 a-35 connects to one of the eNBs via a radio channel, and theeNB has more control functions than the legacy node B. In the LTE systemwhere all user traffic including real time services such as Voice overIP (VoIP) is served through share channels, it is necessary to scheduleUEs based on scheduling information such as buffer status, powerheadroom status, and channel status collected from the UEs, an eNBserving the UEs takes charge of this function.

It is typical that one eNB hosts a plurality of cells. For example, theLTE system adopts Orthogonal Frequency Division Multiplexing (OFDM) as aradio access technology to secure a data rate of up to 100 Mbps in abandwidth of 20 megaHertz (MHz). The LTE system also adopts AdaptiveModulation and Coding (AMC) to determine the modulation scheme andchannel coding rate in adaptation to the channel condition of the UE.

The S-GW 1 a-30 as an entity handling bearers establishes and releasesdata bearers under the control of the MME 1 a-25.

The MME 1 a-25 takes charge of various control functions and maintainsconnections with a plurality of eNBs.

The present disclosure proposes an access control method for determiningwhether to bar an access in a mobile communication system.

If network congestion occurs, the network may limit the number ofinitial access attempts. This is called access barring. The networkbroadcasts predetermined access barring configuration information(hereinafter, referred to as barring configuration information in orderfor each UE to determine its access is barred. On the basis of thebarring configuration information, a UE which wants to access thenetwork determine whether to attempt the access. The present disclosureproposes a service-specific (application-specific) access barringdetermination method of a UE.

FIG. 1B illustrates an access barring determination method in an LTEsystem.

Protocols resided in an LTE UE may be split into first and secondlayers. For example, the first layer may denote an Access Stratum 1b-15, and the second layer may denote a Non-Access Stratum (NAS).

The AS may take charge of all access-related functions. The NAS may takecharge of the other functions such as a service request regardless ofaccess. The access barring determination may be made at the AS of theUE.

As described above, if network congestion occurs, the network may limitinitial accesses by broadcasting access barring configurationinformation to help each UE to make an access attempt decision at step 1b-35. For example, the configuration information may be broadcast insystem information and include at least one of baring configurationinformation, Access Class Barring (ACB) configuration information, ACBskip indicator, Application specific Congestion control for DataCommunication (ACDC) configuration information, and Service SpecificAccess Class (SSAC) configuration information.

In order to meet the requirements newly added to LTE standard, a newaccess barring mechanism has been proposed for performingmultiple-access barring check processes.

The UE NAS may generate a service request to the UE AS at step 1 b-10.If the service request is received, the UE AS determines whether networkaccess is barred.

In detail, if the establishment cause of the service request is set to“delay tolerant access” or a value indicating “delay tolerant access”,the UE AS performs an Extended Access Barring (EAB) check at step 1b-20.

The EAB mechanism is applicable only for Machine Type Communication(MTC). If passing the EAB check, the UE AS performs Application SpecificCongestion control for Data Communication (ACDC) check at step 1 b-22.

The application which requests for a service is assigned an ACDCcategory, and the ACDC category value is included in the service requestbeing transferred to the UE AS.

The network may provide the barring configuration information per ACDCcategory. That is, the barring configuration information may include theinformation on the category of the application as a target of the accesscontrol.

Accordingly, the UE may perform the access check process on theapplication group categorized by the ACDC category. That is, the UE mayperform the access check process based on the category of theapplication which requests for the service. If the barring configurationinformation for the ACDC category is not provided to the network, the UEAS may skip the ACDC access check process.

If passing the ACDC check, the UE AS performs Access Class Barring(ACB). The ACB may denote an access check process performed by the UE ASusing the barring configuration information provided according to MobileOriginating (MO) data or MO signaling. The barring configurationinformation for ACB may be transmitted in the ACB configurationinformation or an SIB to the UE.

In the case of MMTEL voice/video/SMS, however, the UE AS may skip theACB process at step 1 b-25. In this case, the network may transmit anACB skip indicator to skip the ACB check process. Accordingly, the UE ASmay skip the ACB check process based on the ACB skip indicator at step 1b-25.

If it is determined that the access is permitted through the multipleaccess check processes, the UE AS may attempt access to the network.That is, the UE AS performs the random access procedure by transmittinga Radio Resource Control (RRC) Connection Request message at step 1b-40.

There may be an access check process which is not performed by the UEAS. If MMTEL voice/video access barring information (SSAC) is receivedfrom the network at step 1 b-45, the UE AS transfers the access barringinformation to the IMS layer of the UE at step 1 b-50. Here, the SSACbarring information may be transmitted in the SSAC configurationinformation or a SIB to the UE. If the barring configuration informationis received, the IMS layer performs an access barring check process whenthe service is triggered. The SSAC has been designed such that the UE ASperform the function regardless of type of application or service.Accordingly, in order to control the access barring for a specificservice such as MMTEL voice/video, it is necessary to transfer thebarring configuration information to the layer which manages thecorresponding service, thereby the corresponding layer performing theaccess check process.

In the next generation mobile communication system, such complexprocedure is not required. This is because it is possible to implement aconsistent access check process including all requirements introduced inLTE from the initial design stage.

FIG. 1C illustrates an ACDC procedure in an LTE system.

In the LTE system, the ACDC is proposed for the purpose ofapplication-specific (service-specific) access barring determination.Every application is assigned at least one ACDC category value. Forexample, there may be ACDC categories 1 to 16.

The network 1 c-20 may provide the UE 1 c-05 with theapplication-specific ACDC category information using a NAS message. Indetail, the ACDC category information may be delivered to the UE NAS 1c-10 at step 1 c-25. The CDC category information may be included in theACDC configuration information.

The network may transmit ACDC barring configuration information to theUE 1 c-05 at step 1 c-50. In detail, the network 1 c-20 may transmit theACDC category-specific barring configuration information using SIB2.

The barring configuration information may include at least one ofac-BarringFactor Information Element (IE) and an ac-Barringtime IE.Here, the ac-BarringFactor α is selected in the range of 0≤α<1.

The UE 1 c-05 (AS) selects a random value (rand) in the range of0≤rand<1, the random value less than the ac-BarringFactor for indicatingaccess barring and equal to or greater than the ac-BarringFactor forindicating access permission. If it is determined that the access isbarred, the UE AS delays access during a predetermined period calculatedusing equation (1).“Tbarring”=(0.7+0.6*rand)*ac-BarringTime  (1)

If a service request is triggered, the UE (NAS) deduces an ACDC categoryvalue corresponding to the application requesting for the service atstep 1 c-30. The UE NAS may transmit the service request including theACDC category value to the UE AS at step 1 c-35.

Upon receipt of the service request, the UE (AS) may perform the barringcheck. The UE 1 c-05 determine whether the access is barred based on thebarring configuration information included in the SIB2 and the ACDCcategory value of the application requested for the service at step 1c-40.

If the SIB2 includes no barring configuration information correspondingto the ACDC category, it is assumed that the application correspondingto the ACDC category has passed the ACDC process and permitted to accessthe network. If it is permitted to access the network through the accessbarring check process, the UE (AS) transmits an RRC Connection Requestmessage for random access to the network at step 1 c-45.

FIG. 1D illustrates a structure of ACDC configuration information forsue in an LTE system.

The ACDC configuration information may include PLMN-specific barringconfiguration information sets (ACDC-BarringPerPLMN 1,ACDC-BaringPerPLMN 2, . . . ) 1 d-35 and 1 d-40. If all PLMNs have thesame barring configuration information set, the network may broadestcommon barring configuration information set (ACDC-BarringForCommon-r13)1 d-05.

The PLMN-specific barring configuration information set or the commonbarring configuration information set may include per-category barringconfiguration informations 1 d-20, 1 d-25, and 1 d-30. Asaforementioned, the barring configuration information 1 d-45 include theac-BarringFactor IE and ac-Barringtime IE.

Accordingly, the UE may determine whether the access to the network ispermitted based on the barring configuration information and thecategory of the application which has requested for the correspondingservice. If no barring configuration information corresponding to aspecific ACDC category is provided, it is assumed that the applicationwith the corresponding ACDC category is allowed to access the network.

FIG. 1E illustrates an access barring determination method of thepresent disclosure.

The present disclosure is characterized by use of a single consistentbarring mechanism rather than multiple barring mechanism. The proposedbarring mechanism 1 e-20 is implemented on the basis of aservice-specific (application-specific) ACDC.

However, it may also be possible to implement the present disclosure ina such a way of categorizing UE types, call types or slice types ratherthan the application types and barring access from the UE based on otherfactors than application. A detailed description thereof is made later.

The network broadcasts the barring configuration information in thesystem information at step 1 e-25. As described above, the barringconfiguration information may include category-specific information. Thebarring configuration information may include category-specificac-BarringFactor IEs and ac-Barringtime IEs and indicators indicatingcategories for which access is barred.

If a service request is triggered, the UE NAS 1 e-05 may send a servicerequest 1 e-10 to the UE AS 1 e-15. Here, the UE includes theapplication category information in the service request. Every legacyservice or application is assigned at least one category value.

Accordingly, the UE AS determines at step 1 e-20 whether access isbarred based on the barring configuration information and the categoryvalue. According to the present disclosure, the UE may determine whetheraccess is barred for the application which has triggered the servicerequest.

If access is allowed, the UE AS sends an RRC Connection Request messageto the network at step 1 e-30.

FIG. 1F illustrates a structure of access barring configurationinformation according to the present disclosure.

According to the present disclosure may include PLMN-specific barringconfiguration information sets (ACDC-BarringPerPLMN 1,ACDC-BarringPerPLMN 2, . . . ) 1 f-15 and 1 f-20. If all PLMNs have thesame barring configuration information set, the network may broadcast acommon barring configuration information set (ACDC-BarringForCommon) 1f-05.

The PLMN-specific barring configuration information set or the commonbarring configuration information set (ACDC-BarringForCommon) mayinclude per-category barring configuration informations 1 f-50, 1 f-55,and 1 f-60.

As aforementioned, it may be possible to implement the presentdisclosure in such a way of categorizing UE types, call types, or slicetypes rather than the application types.

For example, the legacy ACDC does not provide any barring configurationinformation for MO signaling, MO data, and Emergency signaling. Thepresent disclosure is characterized in that the network further providesthe MO signaling, MO data, and Emergency barring configurationinformations 1 f-25, 1 f-30, and 1 f-40. It may also be possible toprovide the special purposes barring configuration information 1 f-35.It may be possible to define categories for the MO signaling, MO data,and Emergency; the UE NAS may provide the UE AS with dedicated MOsignaling category information when a service request corresponding tothe MO signaling is triggered.

If the MO signaling establishment cause value is transmitted in theservice request to the UE AS before, it may be possible to perform thebarring check using the dedicated MO signaling barring configurationinformation.

As described above, in the present disclosure, it may be possible tocategorize a certain factor rather than application such that the UEdetermines whether access is barred based on the corresponding categoryinformation.

In the legacy system, there is not barring configuration information fora category of a new barring mechanism, it is assumed that access isbarred for the application belonging to the category and thus, althoughthe same barring configuration information is applied to multiplecategories, all per-category configuration informations should beincluded in the system information. This may cause signaling overhead.

The present disclosure is characterized in that if the same barringconfiguration information is applied to multiple categories the commonbarring configuration information 1 f-30 is provided for the multiplecategories to reduce signaling overhead. In the present disclosure, thebarring configuration information which is commonly applied multiplecategories is referred to as common barring configuration or defaultbarring configuration information. Accordingly, the network may includethe common barring configuration information in the system information.

For example, if category 1 and category 2 have the same barringconfiguration information, the network does not include all barringconfiguration informations for the category 1 and category 2 in thesystem information. Instead, the network includes only the commonbarring configuration information in the system information. This isuseful in terms of applying the common barring configuration informationto a specific service.

The UE operation is characterized by making the access barringdetermination based on the common barring configuration informationunlike the legacy technology in which if no barring configurationinformation corresponding to the interesting category exists it isassumed that access is permitted.

Accordingly, the UE may check the service (application) request for thecategory and, if the barring configuration information corresponding tothe category, determine whether access is barred based on the barringconfiguration information, if no barring configuration informationexists, the UE may determine whether access is barred based on thecommon barring configuration information. That is, when there is nobarring configuration information defined for a specific category, itmay be possible to determine whether access is barred based on thecommon barring configuration information. The aforementioned MOsignaling, MO data, and Emergency barring configuration information maybe the common barring configuration information.

The access barring determination is made in such a way of generating arandom value as described above, checking the ac-barringFactor valueincluded in the common barring configuration information, anddetermining whether a random value generated according to a method (tobe described later) is less than the ac-barringFactor value.

It may also be possible to make an access barring determination based ona 1-bit indicator (to be described later) or a specific ac-barringFactorincluded in the common barring configuration information for all servicerequests.

In the case of using the common barring configuration information, theaccess barring check process is performed for every category.Accordingly, there is a need of a method for indicating a category forwhich, if need be, the access barring check process is skipped. Thepresent disclosure proposes a method for indicating the category forwhich access barring check process is skipped with a 1-bit indicator ora specific barring factor (ac-BarringFactor).

In this case, it may be possible to include a 1-bit indicator, insteadof the ac-BarringFactor IE and ac-Barringtime IE, in the barringconfiguration information of the category for which the access barringcheck process is skipped. The UE AS skips the access barring checkprocess, for the category of which barring configuration informationincludes the 1-bit indicator, and assumes that access is permitted. Adescription is made of the method for configuring a specificac-BarringFactor value in detail with reference to FIG. 1G.

The network may also include separate barring configuration informationsin the system information for special purposes or the emergency service.

Accordingly, it may be necessary to define categories dedicated to theemergency service and special purposes respectively in order for the UENAS to provide the UE AS with the category information for the emergencycall or special purposes when a service request for the emergency callor special purposes is triggered.

The separate barring configuration informations may be provided in theform of the ac-BarringFactor IE and ac-Barringtime IE. The barringconfiguration information may also include a 1-bit indicator indicatingwhether to skip the access barring check process. The barringconfiguration information may also include a specific barring factor forskipping the access barring check process for the special purposes oremergency service. This is because typically such services have apriority higher than those of other services.

FIG. 1G illustrates an access barring determination method according tothe present disclosure.

As described above, it may be considered to use a specificac-BarringFactor 1 g-10 of the category for which the access barringcheck process is skipped.

Since the legacy ac-BarringFactor α is the range of 0≤α<1 as denoted byreference numbers 1 g-05 and 1 g-25, it is impossible to skip the accessbarring check process for access permission with no restriction usingthe ac-BarringFactor adjustment method. This is because if a randomvalue generated by the UE AS is in the range of 0≤α<ac-BarringFactor asdenoted by reference number 1 g-20 it is assumed that access ispermitted.

In reference to part (a) of FIG. 1G, if the random value generated bythe UE is in the range of 1 g-20, i.e., equal to or greater than 0 andless than the ac-BarringFactor, access is permitted.

If the random value is in the range of 1 g-25, i.e.,ac-BarringFactor≤α<1 as denoted by reference number 1 g-25, it isassumed that access is barred. In reference to part (b) of FIG. 1G, ifthe random value generated by the UE is equal to or greater thanac-BarringFactor and less than 1 as denoted by reference number 1 g-25,access may be barred.

If ac-BarringFactor is 1 as shown in part (b) of FIG. 1G, the randomvalue generated by the UE is less than ac-BarringFactor and this meansthat access is permitted without any restriction (which is equivalent toskip access barring check process). In the present disclosure, it ispossible to reduce unnecessary ac-BarringTime by skipping the accessbarring check process for a category in such a way of setting theac-BarringFactor included in the corresponding barring configurationinformation to 1. That is, if the barring factor is set to 1, thebarring time value (ac-BarringTime) may not be included in the barringconfiguration information.

FIG. 1H illustrates UE operations according to the present disclosure.

In reference to FIG. 1H, the UE may receive the barring configurationinformation broadcast by an eNB at step 1 h-05.

Next, the UE may trigger a service request for a certain service at step1 h-10. Here, the service request may be triggered by the UE NAS.

The UE may retrieve a category value corresponding to the service atstep 1 h-15. Here, the category value corresponding to the service maybe determined by the UE NAS.

Next, the UE may determine whether access is barred based on the barringconfiguration information at step 1 h-20. The access barringdetermination may be made by the UE AS, and the UE NAS may send theservice request to the UE AS. The service request may include thecategory value.

A description is made of the barring configuration information-basedaccess barring determination method of the UE in detail hereinafter.

FIG. 1I illustrates an access barring determination method of a UEaccording to the present disclosure.

The UE determines at step 1 i-05 whether the triggered service is aspecial purpose or emergency service.

If so, the UE perform an access barring check process on the service atstep 1 i-30. As aforementioned, it may be possible to determine whetheraccess is barred based on separate barring configuration information orto make an access barring process skip determination using a 1-bitindicator.

Otherwise, if the triggered service is a normal service, the UEdetermines at step 1 i-10 whether the barring configuration informationfor the category corresponding to the service has been received from theeNB.

If the barring configuration information for the category correspondingto the service has been received from the eNB, the UE checks thecorresponding barring configuration information for access barringindication. The UE may attempt an access to the service based on theaccess barring indication at step 1 i-25.

Otherwise, if the barring configuration information for the categorycorresponding to the service has not been received from the eNB, the UEchecks the common access barring configuration information for accessbarring indication at step 1 i-20. If the common access barringconfiguration information is not included, the UE skips access barringcheck process. That is, the UE assumes that access is permitted. Next,the UE may attempt access to the service based on the access barringindication at step 1 i-25.

In the present disclosure, steps 1 i-05 and 1 i-30 may be omitted. Asaforementioned, the special purpose or emergency service may becategorized into a dedicated category.

In the present disclosure, the step of determining whether the accessbarring configuration information for the category corresponding to theservice has been received from the eNB may follow step 1 i-15 ofretrieving the category value corresponding to the service. Then, the UEchecks the corresponding configuration information for the case wherethe barring configuration information for the category corresponding tothe service has been received from the eNB and the common access barringconfiguration information for the case where the barring configurationinformation for the category corresponding to the service has not beenreceived from the eNB to acquire the access barring indication.

FIG. J illustrates a configuration of a UE of the present disclosure.

In reference to FIG. 1J, the UE includes a Radio Frequency (RF)processing unit 1 j-10, a baseband processing unit 1 j-20, a memory(storage unit) 1 j-30, and a controller 1 j-40. In the presentdisclosure, the controller 1 j-40 may be interchangeably referred to asa circuit, an application-specific integrated circuit, and at least oneprocessor, and the controller may be coupled with the transceiver.

The RF processing unit 1 j-10 has a function of signal band conversionand amplification for transmitting the signal through a radio channel.That is, the RF processing unit 1 j-10 converts a baseband signal fromthe baseband processing unit 1 j-20 to an RF band signal, the RF bandsignal being transmitted through an antenna, and converts an RF bandsignal received by the antenna to a baseband signal. For example, the RFprocessing unit 1 j-10 may include a transmit filter, a receive filter,an amplifier, a mixer, an oscillator, a Digital to Analog Converter(DAC), and an Analog to Digital Converter (ADC). Although the drawingdepicts one antenna, the UE may be provided with a plurality ofantennas. The RF processing unit 1 j-10 may also include a plurality ofRF chains. The RF processing unit 1 j-10 may perform beamforming. Forbeamforming, the RF processing unit 1 j-10 may adjust phases and sizesof the signals transmitted/received through a plurality of antennas orantenna elements. The RF processing unit 1 j-10 may perform MIMO signalprocessing and receive a signal with multiple layers during the MIMOoperation.

The baseband processing unit 1 j-20 has a function of conversion betweenthe baseband signal and the bitstream according to the physical layerstandard of the system. For example, the baseband processing unit 1 j-20performs encoding and modulation on the transmit bitstream to generatecomplex symbols in the data transmit mode. The baseband processing unit1 j-20 also performs demodulation and decoding on the baseband signalfrom the RF processing unit 1 j-10 to recover the original bitstream inthe data receive mode. In the case of using OFDM, the basebandprocessing unit 1 j-20 performs encoding and modulation on the transmitbitstream to generate complex symbols, maps the complex symbols tosubcarriers, performs Inverse Fast Fourier Transform (IFFT) on themapped symbols, and inserts a Cyclic Prefix (CP) to the IFFTed symbolsto generate OFDM symbols, in the data transmit mode. In the data receivemode, the baseband processing unit 1 j-20 splits the baseband signalfrom the RF processing unit 1 j-10 into OFDM symbols, performs FastFourier Transform (FFT) on the OFDM symbols to recover the signalsmapped to the subcarriers, and performs demodulation and decoding on thesignals to recover the original bitstream.

The baseband processing unit 1 j-20 and the RF processing unit 1 j-10are involved in signal transmission and reception. Accordingly, thebaseband processing unit 1 j-20 and the RF processing unit 1 j-10 may bereferred to as a transmit unit, a receive unit, a transceiver, or acommunication unit. At least one of the baseband processing unit 1 j-20and the RF processing unit 1 j-10 may include a plurality ofcommunication modules for supporting different radio accesstechnologies. At least one of the baseband processing unit 1 j-20 andthe RF processing unit 1 j-10 may also include a plurality ofcommunication modules for processing signals in different frequencybands. For example, the radio access technologies may include a WirelessLocal Area Network (WLAN) technology such as IEEE 802.11 and a cellulartechnology such as LTE. The different frequency bands may include aSuper High Frequency (SHF) band such as 2.5 GHz band and 5 GHz band anda millimeter wave (mmW) band such as 60 Ghz band.

The memory 1 j-30 may store basic programs for operations of the UE,application programs, and setting information. Particularly, the memory1 j-30 may store the information on a secondary access node forperforming radio communication using a secondary radio accesstechnology. The memory 1 j-30 may provide the stored information inresponse to a request from the controller 1 j-40.

The controller 1 j-40 controls overall operations of the UE. Forexample, the controller 1 j-40 transmits/receives signals by means ofthe baseband processing unit 1 j-20 and the RF processing unit 1 j-10.The controller 1 j-40 writes and reads data to and from the memory 1j-40. For this purpose, the controller 1 j-40 may include at least oneprocessor. For example, the controller 1 j-40 may include aCommunication Processor (CP) for controlling communication and anApplication Processor (AP) for controlling higher layer applicationprograms.

In detail, the controller 1 j-40 according to the present disclosure mayreceive the barring configuration information broadcast by an eNB. Thecontroller 1 j-40 may retrieve a category value corresponding to thetriggered service. The controller 1 j-40 may also determine whetheraccess is barred based on the barring configuration information.

In detail, the controller 1 j-40 may determine whether the accessbarring configuration information corresponding to the category of theservice is received. The controller 1 j-40 may also check, when theaccess barring configuration information corresponding to the categoryis received, the access baring configuration information correspondingto the category for the access barring indication and, when the accessbarring configuration information corresponding to the category is notreceived, the common access barring configuration information for theaccess barring indication.

FIG. 1K illustrates a configuration of an eNB of the present disclosure.

As shown in FIG. 1K, the eNB includes an RF processing unit 1 k-10, abaseband processing unit 1 k-20, a backhaul communication unit 1 k-30, amemory 1 k-40, and a controller 1 k-50. In the present disclosure, thecontroller 1 k-50 may be interchangeably referred to as a circuit, anapplication-specific integrated circuit, and at least one processor andthe controller may be coupled with the transceiver.

The RF processing unit 1 k-10 has a function of signal band conversionand amplification for transmitting the signal through a radio channel.That is, the RF processing unit 1 k-10 up-converts a baseband signalfrom the baseband processing unit 1 k-20 to an RF band signal, the RFband signal being transmitted through an antenna, and down-converts anRF band signal received by the antenna to a baseband signal. Forexample, the RF processing unit 1 k-10 may include a transmit filter, areceive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although the drawing depicts one antenna, the eNB may be provided with aplurality of antennas. The RF processing unit 1 k-10 may also include aplurality of RF chains. The RF processing unit 1 k-10 may performbeamforming. For beamforming, the RF processing unit 1 k-10 may adjustphases and sizes of the signals transmitted/received through a pluralityof antennas or antenna elements. The RF processing unit 1 k-10 mayperform MIMO signal processing and receive a signal with multiple layersduring the MIMO operation.

The baseband processing unit 1 k-20 has a function of conversion betweenthe baseband signal and the bitstream according to the physical layerstandard of a primary radio access technology. For example, the basebandprocessing unit 1 k-20 performs encoding and modulation on the transmitbitstream to generate complex symbols in the data transmit mode. Thebaseband processing unit 1 k-20 also performs demodulation and decodingon the baseband signal from the RF processing unit 1 k-10 to recover theoriginal bitstream in the data receive mode. In the case of using OFDM,the baseband processing unit 1 k-20 performs encoding and modulation onthe transmit bitstream to generate complex symbols, maps the complexsymbols to subcarriers, performs IFFT on the mapped symbols, and insertsa Cyclic Prefix (CP) to the IFFTed symbols to generate OFDM symbols, inthe data transmit mode. In the data receive mode, the basebandprocessing unit 1 k-20 splits the baseband signal from the RF processingunit 1 k-10 into OFDM symbols, performs Fast Fourier Transform (FFT) onthe OFDM symbols to recover the signals mapped to the subcarriers, andperforms demodulation and decoding on the signals to recover theoriginal bitstream. The baseband processing unit 1 k-20 and the RFprocessing unit 1 k-10 are involved in signal transmission andreception. For this reason, the baseband processing unit 1 k-20 and theRF processing unit 1 k-10 may be referred to as a transmit unit, areceive unit, a transceiver, or a communication unit.

The backhaul communication unit 1 k-30 provides an interface forintra-node communication. That is, the backhaul communication unit 1k-30 converts the bitstream transmitted from a primary eNB to anothernode (e.g., secondary eNB and core network) to a physical signal andconverts a physical signal received from another node to a bitstream.

The memory 1 k-40 may store basic programs for operations of the eNB,application programs, and setting information. Particularly, the memory1 k-40 may store the information on the bearer allocated to theconnected UE and measurement result reported by the connected UE. Thememory 1 k-40 may also store the information for use in enabling ordisabling multi-connectivity of the UE. The memory 1 k-40 provides thestore data in response to a request from the controller 1 k-50.

The controller 1 k-50 controls overall operations of the primary eNB.For example, the controller 1 k-50 transmits/receives signals by meansof the baseband processing unit 1 k-20 and the RF processing unit 1k-10. The controller 1 k-50 writes and reads data to and from the memory1 k-40. For this purpose, the controller 1 k-50 may include at least oneprocessor.

In detail, the controller 1 k-50 according to the present disclosure maybroadcast barring configuration information. Here, the controller 1 k-50may determine the category barring configuration information per servicecategory and transmit the per-service category barring configurationinformation to the UE. The controller 1 k-50 may also determine a commonbarring configuration information for multiple categories and transmitthe common barring configuration information to the UE. Here, the commonbarring configuration information may be applicable to all categoriesfor which no barring configuration information is specified.

The controller 1 k-50 may also categorize special purpose or emergencyservice into a category and determine the barring configurationinformation for skipping the access barring check process for thecorresponding service. Here, the barring configuration information mayinclude a 1-bit indicator or a predetermined barring factor forinstructing to skip the access barring check process.

Second Embodiment

This embodiment proposes a DRX operation capable of changing a DRX cycleand an inactivity timer dynamically.

FIG. 2A illustrates architecture of an LTE system to which the presentdisclosure is applied. The detailed description of the LTE systemarchitecture has been made already with reference to FIG. 1A and thus isomitted herein.

FIG. 2B is a diagram illustrating a protocol stack of an interfacebetween a UE and an eNB in the LTE system to which the presentdisclosure is applied.

In reference to FIG. 2 , the protocol stack of the interface between theUE and the eNB in the LTE system includes a plurality of protocol layersstacked from the bottom to the top: physical (PHY) layer denoted byreference numbers 2 b-20 and 2 b-25, medium access control (MAC) layerdenoted by reference numbers 2 b-15 and 2 b-30, radio link control (RLC)layer denoted by reference numbers 2 b-10 and 2 b-35, and packet dataconvergence control (PDCP) layer denoted by reference numbers 2 b-05 and2 b-40.

The PDCP layer denoted by reference numbers 2 b-05 and 2 b-40 takescharge of compressing/decompressing an IP header. The main functions ofthe PDCP layer are as follows:

-   -   Header compression and decompression (ROHC only);    -   Transfer of user data;    -   In-sequence delivery of upper layer PDUs at PDCP        re-establishment procedure for RLC AM;    -   For split bearers in DC (only support for RLC AM);    -   PDCP PDU routing for transmission and PDCP PDU reordering for        reception);    -   Duplicate detection of lower layer SDUs at PDCP re-establishment        procedure for RLC AM;    -   Retransmission of PDCP SDUs at handover and, for split bearers        in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM;    -   Ciphering and deciphering;    -   Timer-based SDU discard in uplink.

The RLC layer denoted by reference numbers 2 b-10 and 2 b-35 takescharge of segmenting a PDCP PDU into segments of appropriate size forAutomatic Repeat Request (ARQ) operation. The main functions of the RLClayer are as follows:

-   -   Transfer of upper layer PDUs;    -   Error Correction through ARQ (only for AM data transfer);    -   Concatenation, segmentation and reassembly of RLC SDUs (only for        UM and AM data transfer);    -   Re-segmentation of RLC data PDUs (only for AM data transfer);    -   Reordering of RLC data PDUs (only for UM and AM data transfer);    -   Duplicate detection (only for UM and AM data transfer);    -   Protocol error detection (only for AM data transfer);    -   RLC SDU discard (only for UM and AM data transfer);    -   RLC re-establishment.

The MAC layer denoted by reference number 2 b-15 and 2 b-30 allows forconnection of multiple RLC entities established for one UE and takescharge of multiplexing RLC PDUs from the RLC layer into a MAC PDU anddemultiplexing a MAC PDU into RLC PDUs.

-   -   Mapping between logical channels and transport channels;    -   Multiplexing/demultiplexing of MAC SDUs belonging to one or        different logical channels into/from transport blocks (TB)        delivered to/from the physical layer on transport channels;    -   Scheduling information reporting;    -   Error correction through HARQ;    -   Priority handling between logical channels of one UE;    -   Priority handling between UEs by means of dynamic scheduling;    -   MBMS service identification;    -   Transport format selection;    -   Padding.

The PHY layer denoted by reference numbers 2 b-20 and 2 b-25 takescharge of channel-coding and modulation on higher layer data to generateand transmit OFDM symbols over a radio channel, and demodulating andchannel-decoding on OFDM symbols received over the radio channel, thedecoded data being delivered to the higher layers.

FIG. 2C illustrates a DRX operation.

DRX is a technique of monitoring Physical Downlink Control Channel(PDCCH) for scheduling information only during a predetermined period tominimize power consumption of a UE. DRX is applicable in idle andconnected modes but with slight difference. The present disclosure isdirected to the operation in the connected mode. However, the presentdisclosure is not limited thereto but can be applied to the operation inthe idle mode.

If a UE stays awake all the time to monitor PDCCH for acquiringscheduling information, this may cause high power consumption. A basicDRX operation has a DRX cycle 2 c-00 and the UE monitors PDCCH onlyduring the on-duration period 2 c-05 within the DRX cycle 2 c-00.

In the connected mode, at least one of a long DRX and short DRX cyclescan be configured. In normal operation, the long DRX cycle is appliedand, if need be, the eNB may trigger the short DRX cycle using a MACControl Element (CE). After a predetermined time period, the UE maychange the short DRX cycle for the long DRX cycle. The initialscheduling information of a certain UE is transmitted on a predeterminedPDCCH. The UE monitors PDCCH periodically to minimize power consumption.

If the scheduling information for a new packet is received on the PDCCHduring the on-duration period 2 c-05, the UE starts a DRX inactivitytimer as denoted by reference number 2 c-15. The UE remains in theactive state while the DRX inactivity timer is running. That is, the UEcontinues monitoring PDCCH. The UE also starts a HARQ Round Trip Time(RTT) timer as denoted by reference number 2 c-20. The HARQ RTT timer isapplied to protect against unnecessary PDCCH monitoring during the HARQRTT and thus it is not necessary for the UE to monitor PDCCH while theHARQ RTT timer is running. However, while both the DRX inactivity timerand HARQ RTT timer are running, the UE monitors PDCCH until the DRXinactivity timer expires.

If the HARQ RTT timer expires, a DRX retransmission timer starts asdenoted by reference number 2 c-25. While the DRX retransmission isrunning, the UE has to monitor PDCCH. Typically, the schedulinginformation for HARQ retransmission is received while the DRXretransmission timer is running as denoted by reference number 2 c-30.If the scheduling information is received, the UE stops the DRXretransmission timer immediately and starts the HARQ RTT timer again.The above process is repeated until the packet is received successfullyas denoted by reference number 2 c-35.

The configuration information related to the DRX operation in theconnected mode is transmitted in an RRC Connection Reconfiguration(RRCConnectionReconfiguration) message to the UE. Each of theon-duration timer, the DRX inactivity timer, and the DRX retransmissiontimer corresponds to a number of subframes. If a predetermined number ofPDCCH subframes arrive after the start of a timer, the timer expires. InFrequency Division Duplex (FDD), all downlink subframes are PDCCHsubframes; in Time Division Duplex (TDD), downlink and special subframesare PDCCH subframes. In TDD, the downlink, uplink, and special subframesexist in the same frequency band. Among them, the downlink and specialsubframes are regarded as PDCCH subframes.

The eNB may configure two DRX states: longDrx and shortDRX. The eNB mayuse one of the two DRX states in consideration of power preferenceindication information reported by the UE, UE mobility log information,and characteristic of configured DRB. The transition between the twostates is triggered by expiry of a certain timer or transmission of apredetermined MAC CE from the eNB to the UE.

However, only with the two DRX cycles specified in LTE, it is difficultyto adjust the length of the DRX cycle dynamically according to DRBcharacteristics, traffic pattern, and buffer status.

The present disclosure proposes a DRX operation capable of adjusting thelength of the DRX cycle or drx-InactivityTimer dynamically according tothe DRB characteristics, traffic pattern, and buffer status. here, theDRB characteristics, traffic pattern, and buffer status may be referredto as data communication information. That is, in the presentdisclosure, the eNB may adjust the DRX cycle or a timer valuedynamically according to the data communication information.

Particularly, the eNB configures a default DRX cycle or a default DRXinactivity timer (drx-InactivityTimer) to the UE and adjust the lengthof the DRX cycle dynamically using a MAC CE. The present disclosure alsoproposes a method of stopping DRX operation, upon receipt of a beammeasurement report (particularly a new best beam report), andmaintaining the active time.

FIG. 2D illustrates the concept of a DRX operation in the connected modeaccording to the present disclosure.

In the present disclosure, the eNB may configure a DRX functionalitywith a default DRX cycle and a default drx-InactivityTimer to the UE. Inthe present disclosure, the DRX cycle and the DRX-related timer valuewhich the eNB initially configures to the UE may be referred to asinitial DRX cycle and initial DRX-related timer, and the eNB mayconfigure at least one initial DRX cycle and at least one initialDRX-related timer to the UE. Here, examples of the DRX-related timerinclude the aforementioned drx-InactivityTimer anddrx-retransmissionTimer.

If the DRX functionality is configured to the UE, the UE starts the DRXoperation at a predetermined time point. The DRX operation starts withthe default DRX cycle 2 d-10. The UE monitors a control channel duringthe onDuration period 2 d-05 of every cycle. The control channel mayinclude downlink or uplink scheduling information for the UE. TheonDuration period is also configured by the eNB.

Meanwhile, the eNB may check for DRB characteristics, traffic pattern,buffer status, and frame structure as denoted by reference number 2d-15. If it is necessary to apply a shorter DRX cycle, the eNB mayadjust the DRX cycle as denoted by reference numbers 2 d-30 and 2 d-40and drx-InactivityTimer values as denoted by reference numbers 2 d-25and 2 d-35 using a predetermined MAC CE 2 d-20. The MAC CE includes newDRX cycle or drx-InactivityTimer value. Here, the MAC CE carrying theDRX cycle or drx-InactivityTimer value may be referred to as DRXreconfiguration information, and the information being changed by theMAC CE may be referred to as DRX parameters. Although the description isdirected to the case where the DRX cycle or DRX-related timer values arechanged by means of a MAC CE, the present disclosure is not limitedthereto. For example, the eNB may use a MAC CE to change otherDRX-related information (DRX parameter) included in the DRXconfiguration information as well as the DRX cycle and DRX-related timervalues.

The new parameter values may be provided in various ways as follows.Although this embodiment is directed to a case where thedrx-InactivityTimer value is changed for convenience of explanation, thepresent disclosure is not limited to this embodiment. That is, thepresent disclosure can be applied to change any of all DRX-related timervalues.

-   -   Option 1: The MAC CE may include information on the multiples of        the default DRX cycle and default drx-InactivityTimer values,        e.g., ¼, ½, 2, 4, 6, and 8 (or indices corresponding to        respective multiples) of the default DRX cycle and default        drx-InactivityTimer values.    -   Option 2, The MAC CE may include absolute values of the DRX        cycle and default drx-InactivityTimer values to be applied (or        indices corresponding to the absolute values).

In the case of applying Option 1, the eNB transmits the information onthe multiples of the default DRX cycle and default drx-InactivityTimeror indices corresponding to the multiples in a MAC CE to the UE, and theUE may acquire the DRX cycle and timer values based on the default DRXcycle and default drx-InactivityTimer values and the informationcontained in the MAC CE. The information on the multiple of the defaultDRX cycle value and the information on the multiple of the defaultdrx-InactivityTimer value may be configured separately and differently.Also, the information on the multiple of the default DRX cycle value andthe information on the multiples of the default drx-InactivityTimervalue may be configured identically.

Also, the eNB may change one of the default DRX cycle and defaultdrx-InactivityTimer values by transmitting to the UE the information onthe multiples of one of the default DRX cycle and defaultdrx-InactivityTimer values in the MAC CE.

For example, if the MAC CE includes a value of ¼, the UE applies the DRXcycle corresponding to ¼ of the default DRX cycle. If it is configuredto apply the information on the multiple to the default DRX cycle anddefault drx-InactivityTimer values identically, the UE may apply theinactivity timer value of ¼ of the default drx-InactivityTimer.

If the information on the multiple of the default DRX cycle value andthe information on the multiples of the default drx-InactivityTimervalue are configured separately, the UE may not change the value of thedefault drx-InactivityTimer.

In the case of applying Option 2, the eNB may include at least one ofthe DRX cycle and drx-InactivityTimer values in the MAC CE. The UE mayoperate with the DRX cycle and drx-InactivityTimer values contained inthe MAC CE.

In the present disclosure, the eNB may configure two or more DRX-relatedtimer values to the UE and change the DRX-related timer values using theMAC CE.

Typically, if a short DRX cycle is applied, this is the case where theinter-arrival time (difference of arrival times of packets) is shortenedin the traffic pattern. In the next generation mobile communicationsystem, even the frame structure may be changed depending the purpose.For example, it is required to shorten the delay time, the TransmissionTime Interval (TTI) may decrease. This means the decrease of RRT. Here,it may be possible to reduce power consumption of the UE withoutperformance degradation even when applying the shorterdrx-InactivityTimer.

The new parameter values may be applied immediately or at apredetermined time point after the receipt of the MAC CE. It may bepossible to define a new MAC CE for triggering the DRX operation.

The predetermined time point may be configured by the eNB orpreconfigured at the UE. The time point may be indicated by the numberof subframes arriving since the receipt of the MAC CE.

The newly applied values are valid during a predetermined time period oruntil a predetermined event occurs. If the predetermined period expiresor the predetermined event occurs, the parameters are initialized to thedefault values or updated to new values.

The predetermined time period may be configured by the eNB andtransmitted to the UE. The predetermined time period may be provided inthe form of a timer or a multiple of the default DRX cycle. Thepredetermined time period may also be fixed with a predetermined value.The applied value may be initialized to the default value or updated toa new value.

If any of DRB characteristics, traffic pattern, buffer status, and framestructure changes as denoted by reference number (2 d-55), and a MAC CE(2 d-50) including new values is received, the UE applies the new valuesas denoted by reference numbers 2 d-35 and 2 d-40. If a MAC CEinstructing to initialized to the default values is received, the UEapplies the default values.

FIG. 2E illustrates signal flows in a DRX procedure for a UE accordingto the present disclosure.

The UE 23-05 may receive DRX configuration information from an eNB 2e-10 at step 2 e-15.

If the DRX cycle and drx-InactivityTimer values to be applied are notthe default DRX cycle and default drx-InactivityTimer values, the DRXconfiguration information includes at least one of a timer value (or amultiple of the default DRX instead of the timer value) and the starttime point for applying the non-default values.

If the DRX configuration information is received, the UE 2 e-05 startsthe DRX operation based on the configuration information immediately asdenoted by reference number 2 e-22 or at a predetermined time point.Alternatively, the eNB 2 e-10 may transmit to the UE 2 e-05 a MAC CE(which is newly defined for triggering the DRX operation) at 2 e-20. Inthis case, the UE may perform the DRX operation immediately upon receiptof the new MAC CE or at a predetermined time point.

Next, the eNB 2 e-10 may calculate the best DRX cycle ordrx-InactivityTimer values based on various informations such as DRBcharacteristics, traffic pattern, buffer status, and frame structure atstep 2 e-25.

The UE 2 e-05 may collect the information on the DRX characteristics,traffic pattern, and buffer status at step 2 e-30 and transmits theinformation to the eNB 2 e-10 at step 2 e-35 in order to help the eNB togenerate the best DRX configuration information.

If it is determined to reset the DRX cycle or DRX-related time to a newvalue instead of the current default value, the eNB 2 e-10 transmits aMAC CE including the new value to the UE 2 e-05 at step 2 e-40.

As described above, the eNB 2 e-10 may transmit the MAC CE including theinformation on a multiple of at least one of the DRX cycle andDRX-related timer values to the UE 2 e-05. As described above, themultiple of the DRX cycle value and the multiple DRX-related timer valuemay be configured independently. The eNB 2 e-10 may transmit to the UE 2e-05 the MAC CE including at least one of the DRX cycle value and theDRX-related timer value.

If the MAC CE is received, the UE 2 e-05 applies the newly configuredvalue immediately or at a predetermined time point. The information onthe predetermined time point may be configured based on the DRXconfiguration information or preconfigured by the UE 2 e-05.

The UE 2 e-05 applies the newly configured value to the DRX operation atstep 2 e-45 during a predetermined time period or until a predeterminedevent occurs. Here, the values configured newly based on the informationincluded in the MAC CE may be referred to as temporary DRX cycle valueand temporary DRX-related timer value.

The eNB 2 e-10 may transmit to the UE 2 e-05 the MAC CE to apply thedefault values or newly configured values at step 2 e-50. If the MAC CEis received from the eNB 2 e-10, the UE 2 e-05 updates the DRX cycle orinitialize the DRX cycle to the default value at step 2 e-55.

FIG. 2FA illustrates a DRX operation of a UE according to the presentdisclosure.

The UE receives the DRX configuration information from the eNB at step 2f-05. As described above, if the DRX cycle and drx-InactivityTimervalues to be applied are not the default DRX cycle and defaultdrx-InactivityTimer values, the DRX configuration information includesat least one of a timer value (or a multiple of the default DRX insteadof the timer value) and the start time point for applying thenon-default values.

After receiving the DRX configuration information, the UE starts the DRXoperation at a predetermined time point at step 2 f-10. The eNB maytransmit a MAC CE for triggering the DRX operation, and the UE mayperform the DRX operation immediately upon receipt of the MAC CE or at apredetermine time point.

The UE receives a DRX MAC CE (or DRX configuration information) at step2 f-15. This MAC CE may include the configuration information forupdating DRX parameters. This MAC CE may include a multiple of at leastone of the DRX cycle and DRX-related timer values or new DRX cycle anddrx-InactivityTimer values.

If the new DRX configuration information is received, the UE stops thecurrently-running onDurationTimer and drx-InactivityTimer at step 2f-20.

The UE applies the new parameter values immediately upon receipt of theMAC CE or at a predetermined time point. Here, the predetermined timepoint may be configured based on the DRX configuration information orpreconfigured by the UE, and detailed description thereof has been madeabove and thus is omitted herein.

The UE initializes the parameters to the default values or updates theparameters to new values at step 2 f-30 after a predetermined timeperiod or when a predetermined event occurs. In detail, the UE mayinitialize the DRX cycle and drx-related timer to default values when apredetermined time period expires. The eNB may transmit a MAC CE, andthe UE may update or initialize the DRX cycle and DRX-related timer todefault values based on the information included in the MAC CE.

FIG. 2FB illustrates a DRX operation of an eNB according to the presentdisclosure.

The eNB transmits DRX configuration information to the UE at step 2f-35. As described above, if the DRX cycle and drx-InactivityTimervalues to be applied are not the default DRX cycle and defaultdrx-InactivityTimer values, the DRX configuration information includesat least one of a timer value (or a multiple of the default DRX insteadof the timer value) and the start time point for applying thenon-default values.

The eNB calculates the best DRX parameters (DRX cycle anddrx-InactivityTimer) values based on various informations such as DRBcharacteristics, traffic pattern, buffer status, and frame structure atstep 2 f-40.

The eNB may transmit a DRX MAC CE (or DRX configuration information) tothe UE. This MAC CE may include the configuration information forupdating DRX parameters. This MAC CE may include a multiple of at leastone of the DRX cycle and DRX-related timer values or new DRX cycle anddrx-InactivityTimer values.

The UE applies new the parameter values immediately upon receipt of theMAC CE or at a predetermined time point. If a predetermined time periodelapses or an event occurs, the UE applies the default values or newvalues. Here, the eNB may update or initialize the DRX parameters todefault values by transmitting a MAC CE to the UE.

It may be considered for the eNB to transmit the DRX configurationinformation including two or more timer values for updating theDRX-related timer and instruct the UE to select and use one of the timervalues by transmitting a MAC CE.

FIG. 2G illustrates MAC CE formats according to the present disclosure.The present disclosure proposes new MAC CE formats for providing newvalues.

Option A—1-Byte Structure

The first method is to use a 1-byte (8-bit) MAC CE format as shown inupper part of FIG. 2G. The 8-bit MAC CE format carries relative valuesof the DRX cycle and drx-InactivityTimer.

In detail, the first bit 2 g-05 of the 8 bits indicates whether the MACCE carries a relative DRX cycle value. For example, this bit is set to 0for indicating no inclusion of the relative DRX cycle value or 1 forindicating inclusion of the relative DRX cycle value.

The second bit 2 g-10 of the 8 bits indicates whether the MAC CE carriesa relative drx-InactivityTimer value. For example, this bit is set to 0for indicating no inclusion of the relative drx-InactivityTimer value or1 for indicating inclusion of the relative drx-InactivityTimer value.

In this way, the eNB may configure the DRX cycle and drx-InactivityTimervalues respectively. Three bits among the remaining bits are used toindicate the relative DRX cycle value. For example, if the new value isone of the multiples (i.e., ⅛, ⅙, ¼, ½, 2, 4, 6, and 8) of the defaultvalue, the index of each multiple may be indicated by 3 bits. That is,the multiples may be mapped to the respective indices as follows.

b5 (b2) b4 (b1) b3 (b0) New value 0 0 0 Default × ⅛ 0 0 1 Default × ⅙ 01 0 Default × ¼ 0 1 1 Default × ½ 1 0 0 Default × 2 1 0 1 Default × 4 11 0 Default × 6 1 1 1 Default × 8

The remaining 3 bits 2 g-20 are used to indicate the relativedrx-InactivityTimer value. For example, if the new value is one of themultiples (i.e., ⅛, ⅙, ¼, ½, 2, 4, 6, and 8) of the default value, theindex of each multiple may be indicated by 3 bits.

If the two bits which are designated for use in determining whether theMAC CE carries the relative DRX cycle and drx-InactivityTimer values areall set to 0, this may indicate initialization to the default values.

The bit positions designated for the respective purposes may be changedin the 1-byte structure. The reason for use of the two most significantbits 2 g-05 and 2 g-10 for the purpose of indicatinginclusion/non-inclusion of the relative DRX cycle anddrx-InactivityTimer values in the MAC CE format is to determine, withpriority, whether to perform decoding on the bits following the twobits.

The three bits 2 g-15 or 2 g-20 may indicate an absolute value ratherthan a relative value. Here, at least the absolute value is notidentical with default value. The absolute value may be derived from amultiple of the default value.

In the present disclosure, it may be possible to update other parametersthan the DRX cycle and drx-InactivityTimer using the multiple valueinformation or absolute values. In this case, it may be possible toincrease the number of bits of the MAC CE for other parameters, decreasethe number of bits for relative multiple value information indicationfiled to 2 bits to carry the multiple value information for the otherDRX parameters, or use one of the DRX cycle and drx-InactivityTimerindication fields for other DRX parameters.

Option B—2-Byte Structure

The second method is to use a 2-byte (16-bit) MAC CE format as shown inlower part of FIG. 2G. The 16-bit MAC CE format carries relative valuesof the DRX cycle and drx-InactivityTimer.

In detail, the first bit 2 g-25 of the first byte indicates whether theMAC CE carries a relative DRX cycle value. For example, this bit is setto 0 for indicating no inclusion of the relative DRX cycle value or 1for indicating inclusion of the relative DRX cycle value.

Also, the first bit 2 g-35 of the second byte indicates whether the MACCE carries a relative drx-InactivityTimer value. For example, this bitis set to 0 for indicating no inclusion of the relativedrx-InactivityTimer value or 1 for indicating inclusion of the relativedrx-InactivityTimer value.

In this way, the eNB may configure the DRX cycle and drx-InactivityTimervalues respectively. The 7 remaining bits 2 g-40 of the first byte isused to carry the relative DRX cycle value. Here, the index indicating amultiple value (multiple value information) may be carried in the 7bits. The 7 bits may carry an absolute value rather than the relativevalue.

Also, the 7 remaining bits 2 g-45 of the second byte is used to carrythe relative drx-InactivityTimer value. Here, the index indicating amultiple value (multiple value information) may be carried in the 7bits. The 7 bits may carry an absolute value rather than the relativevalue.

As described above, if the first bits of the first and second byteswhich are designated for use in determining whether the MAC CE carriesthe relative DRX cycle and drx-InactivityTimer values are all set to 0,this may indicate initialization to the default values.

The bit positions designated for the respective purposes may be changedin the 2-byte structure. The reason for use of the most significant bits2 g-25 and 2 g-35 of the first and second bytes for the purpose ofindicating inclusion/non-inclusion of the relative DRX cycle anddrx-InactivityTimer values in the MAC CE format is to determine withpriority whether to perform decoding on the bits following the two bits.

In the present disclosure, it may be possible to update other parametersthan the DRX cycle and drx-InactivityTimer using the multiple valueinformation or absolute values. In this case, it may be possible toincrease the number of bits of the MAC CE for other parameters, decreasethe number of bits for relative multiple value information indicationfiled to 2 bits to carry the multiple value information for the otherDRX parameters, or use one of the DRX cycle and drx-InactivityTimerindication fields for other DRX parameters.

FIG. 2H illustrates a best beam pair according to the presentdisclosure.

In the next generation mobile communication system, it may be possibleto use a beam antenna optimized for very narrow frequency bandwidth. Thebeamforming may be used by a UE 2 h-05 as well as an eNB 2 h-10. It maybe possible to form multiple beams at different angles totransmit/receive signals in respective directions. The eNB and UEsignore all but the beams formed for transmitting and receiving signalsthereto and therefrom. Although beams are formed in other directions fortransmitting/receiving data, it is difficult to expect any performanceimprovement because of very low beam antenna gain. Instead, the beamsforming in other directions are likely to cause interference to otherUEs and/or eNBs.

In the present disclosure, one of the eNB and the UE has to form a beamin a direction to the other for data transmission/reception, and thesebeams are called best beam pair.

In reference to FIG. 2H, it is expected that the largest beam antennagain is achieved with the first beam 2 h-15 of the UE B which is formedtowards the eNB and the ninth beam 2 h-20 of the eNB which is formedtowards the UE B. In this case, it can be told that the two beams are inthe state of the best beam pair as denoted by reference number 2 h-25.

Meanwhile, as the UE moves, the best beam pair may be changed. In orderto maximize the data communication efficiency, it is required tomaintain the best beam pair regardless of the movement of the UE. Thebest beam pair is determined through beam measurement performed by theUE or eNB performs on its own beam or counterpart's beam.

That is, the UE transmits beam measurement information about the beamwith the largest signal strength gain to the eNB, and the eNB transmitsbeam configuration information (BCC) to the UE to notify the UE of thebest beam pair for data communication. If the best beam pair changes asthe UE moves, the eNB may notify the UE of the changed best beam pair.Here, the best beam pair reconfiguration procedure should be completedas soon as possible to protect against performance degradation.

However, if the UE is in the DRX mode, the best beam pairreconfiguration procedure may be delayed.

FIG. 2I illustrates a DRX operation in the beam measurement resultreport process according to the present disclosure.

The UE performs beam measurement during the onDuration period 2 i-02within one DRX cycle 2 i-05 for power saving.

The UE may identify that the current beam pair is not the best beam pairfor data communication as denoted by reference number 2 i-10.

If the UE becomes aware that the current beam pair is not the best beampair for data communication, it has to report this to the eNB. Since thebest beam pair reconfiguration should be completed as soon as possible,the UE reports a new beam measurement result (best beam) to the eNBimmediately ignoring the DRX cycle as denoted by reference number 2i-15. That is, the UE may stop the DRX operation and report the beammeasurement result to the eNB in the active state.

The eNB is supposed to reconfigure the best beam pair upon receipt ofthe report, the UE waits for the best beam pair reconfiguration. If theeNB provides the UE with the beam reconfiguration information in linewith the DRX cycle, this may cause a delay as much as the maximum DRXcycle. The present disclosure makes it possible for the UE to report thebeam measurement result to the eNB regardless of the DRX cycle. The beammeasurement result may include the information indicating that the bestbeam has been changed or the changed best beam information (BBI). If itis scheduled to receive beam configuration information from the eNB, theUE stops or suspends the DRX operation during a predetermined timeperiod or until a predetermined event occurs, e.g., the beamconfiguration information is received from the eNB as denoted byreference number 2 i-25. During the DRX operation suspension period, theUE remains in the Active Time state.

While the Active Time state is maintained, the UE may perform the beammeasurement regardless of the DRX cycle. The predetermined time periodmay be configured by the eNB or predetermined. The time period isdetermined in consideration of the RTT and the processing time of theeNB so as to be a value longer than the RTT.

If the predetermined time period expires or if the predetermined eventoccurs, the UE resumes the DRX operation immediately or at apredetermined time point as denoted by reference number 2 i-30. Here,the predetermined event may be the event of receiving the beamconfiguration information, and the UE may determine the best beam basedon the beam configuration information and resume the DRX operationimmediately or at a predetermined time point.

FIG. 2J illustrates a beam measurement result report procedure accordingto the present disclosure.

The UE 2 j-05 and the eNB 2 j-10 check for beam-based functionsupportability at step 2 j-15.

In detail, the UE 2 j-05 reports its beam-based function capability in apredetermined RRC message to the eNB 2 j-10. For example, the UE maytransmit UE capability information (UECapability information) in the RRCmessage to the eNB 2 j-10.

Also, the eNB 2 j-10 may broadcast its beam-based functionsupportability in the system information to the UEs within its servicearea.

The eNB 2 j-10 transmits to the UE 2 j-01 at least one of beam-basedmeasurement configuration information and DRX configuration informationin an RRC message at step 2 j-20.

Upon receipt of the RRC message, the UE applies the configurationinformation to perform beam measurement and DRX operations at step 2j-25.

As described above, the DRX operation may start after receiving apredetermined MAC CE at step 2 j-30. However, the present disclosure isnot limited thereto but may include starting, at the UE 2 j-05, the DRXoperation after a predetermined time period (a predetermined number offrames) after the receipt of the DRX configuration.

The UE 2 j-05 performs measurement on multiple beams form the eNB 2j-10. It may be determined that the current beam pair is not the bestbeam pair based on the beam measurement result.

Accordingly, the UE 2 j-05 may identify the change of the best beam pairbases on the beam measurement result at step 2 j-35. The UE may adjustthe current beam pair to maintain the best beam pair and report bestbeam information (best beam indication) to the eNB 2 j-10 at step 2j-40.

Then the UE 2 j-05 suspends the DRX operation and remains in the ActiveTime state at step 2 j-45. The UE 2 j-05 reports the best beaminformation to the eNB 2 j-10 and stops the currently-running DRXoperation.

Next, the UE 2 j-05 may receive new beam configuration information (orbeam change command) from the eNB 2 j-10 at step 2 j-50. If apredetermined time period expires or the new beam configurationinformation is received from the eNB 2 j-10 at step 2 j-50, the UE 2j-05 may apply the new best beam pair at step 2 j-55.

Then, the UE 2 j-05 resumes the DRX operation at step 2 j-60.

FIG. 2KA illustrates UE operations in the beam measurement result reportprocedure according to the present disclosure.

The UE may transmit an RRC message including the UE capabilityinformation to the eNB to notify the eNB of its beam-based functioncapability. The UE may acquire the beam-based function supportability ofthe eNB from the system information broadcast by the eNB. In this way,the UE and the eNB may check for the beam-based functions they cansupport.

The UE may receive at least one of the beam measurement configurationinformation and DRX configuration information from the eNB at step 2k-05. The UE may acquire the configuration information from an RRCmessage transmitted by the eNB.

The UE receives the configuration information and starts beammeasurement and DRX operations immediately or at a predetermined timepoint at step 2 k-10. The information on the beam measurement and DRXoperation start time point may be included in the configurationinformation. The UE may start the beam measurement and DRX operationafter receipt of a MAC CE.

Next, the UE perform beam measurement periodically to check for changeof the best beam pair at step 2 k-15.

The UE may report the change of the best beam pair to the eNB, suspendthe currently running DRX operation, and maintain the Active Time atstep 2 k-20. Here, the UE may transmit the best beam information to theeNB. The UE may also transmit to the eNB the information indicating thatthe best beam pair has been changed.

The UE maintains the Active Time during a predetermined time period oruntil a predetermined even occurs and then resumes the DRX operationimmediately or at a predetermined time point at step 2 k-25.

As described above, the predetermined event may be receiving the newbeam configuration information from the eNB. The UE may receive theinformation on the new best beam pair from the eNB and resume the DRXoperation.

The information on the predetermined time period concerning the resumeof the DRX operation may be included in the DRX configurationinformation, and the UE may resume the DRX operation after thepredetermined time period expires.

FIG. 2KB illustrates eNB operations in the beam measurement resultreport procedure according to the present disclosure.

The eNB may acquire the UE capability information from an RRC messagetransmitted by the UE to check fur the beam-based function capability ofthe UE. The eNB may broadcast its beam-based function supportability inthe system information.

The eNB may transmit at least one of the beam measurement configurationinformation and the DRX configuration information at step 2 k-35. TheeNB may transmit the configuration information in an RRC message.

Then, the eNB may transmit a MAC CE for triggering a DRX operation ofthe UE at step 2 k-40. However, the step of transmitting the MAC CE maybe omitted if the information on the DRX start time point is included inthe DRX configuration information or predetermined.

If the best beam pair is changed, the eNB may receive the information onthe best beam at step 2 k-45. The eNB may also receive the informationindicating that the best beam pair has been changed.

Then, the eNB may transmit new beam configuration information indicatingthe new best beam pair to the UE at step 2 k-50.

FIG. 2L illustrates a configuration of a UE according to the presentdisclosure.

In reference to FIG. 2L, the UE includes an RF processing unit 2 l-10, abaseband processing unit 2 l-20, a memory 2 l-30, and a controller 2l-40. In the present invention, the controller 2 l-40 may beinterchangeably referred to as a circuit, an application-specificintegrated circuit, and at least one processor and the controller may becoupled with the transceiver.

The RF processing unit 2 l-10 may perform the same function as the RFprocessing unit 1 j-10 of FIG. 1J and thus detailed description thereofis omitted herein.

The baseband processing unit 2 l-20 may perform the same functions asthe baseband processing unit 1 j-20 of FIG. 1J and thus detaileddescription thereof is omitted herein.

The baseband processing unit 2 l-20 and the RF processing unit 2 l-10are involved in signal transmission and reception as described above.Accordingly, the baseband processing unit 2 l-20 and the RF processingunit 2 l-10 may be referred to as a transmit unit, a receive unit, atransceiver, or a communication unit. The detailed description thereofhas been described with reference to FIG. 1J and thus omitted herein.The memory 2 l-30 may be identical in functionality with the memory 1j-30 as described with reference to FIG. 1J and thus detaileddescription thereof is omitted herein.

The controller 2 l-40 controls overall operations of the UE. Forexample, the controller 2 l-40 transmits/receives signals by means ofthe baseband processing unit 2 l-20 and the RF processing unit 2 l-10.The controller 2 l-40 writes and reads data to and from the memory 2l-40. For this purpose, the controller 2 l-40 may include at least oneprocessor and the controller may be coupled with the transceiver. Forexample, the controller 2 l-40 may include a Communication Processor(CP) for controlling communication and an Application Processor (AP) forcontrolling higher layer application programs.

In detail, the controller 2 l-40 may control the UE to transmit an RRCmessage including the UE capability information to the eNB to notify theeNB of its beam-based function capability. The controller 2 l-40 mayalso control the UE to acquire the information on the beam-basedfunction supportability of the eNB from the system information broadcastby the eNB. In this way, the UE and the eNB may check for the beam-basedfunctions which they support. The controller 2 l-40 may control the UEto receive DRX configuration information.

The controller 2 l-40 may control the UE to start a DRX operationimmediately upon receipt of the DRX configuration information or at apredetermined time point after the receipt of the DRX configurationinformation. The controller 2 l-40 may also control the UE to performthe DRX operation immediately upon receipt of the MAC CE or at apredetermined time point after the receipt of the MAC CE.

The controller 2 l-40 may also control the UE to receive a DRX MAC CE(or DRX reconfiguration information). The DRX MAC CE may includeconfiguration information for changing DRX parameters. This MAC CE mayinclude a multiple of at least one of the DRX cycle and DRX-relatedtimer values or new DRX cycle and drx-InactivityTimer values.

If the new DRX reconfiguration information is received, the controller 2l-40 may stop the currently running onDurationTimer anddrx-InactivityTimer.

The controller 2 l-40 applies the new parameter values immediately uponreceipt of the MAC CE or at a predetermined time point. Afterward, thecontroller 2 l-40 applies the default values or newly selected valueswhen a predetermined time period expires or a predetermined eventoccurs. In detail, the UE may apply the default DRX period and defaultDRX-related timer value when the predetermined time period expires.Also, the UE may transmit a MAC CE, and the UE may update or initializethe DRX cycle and DRX-related timer to default values based on theinformation included in the MAC CE.

According to an alternative embodiment, the controller 2 l-40 maycontrol the UE to receive at least one of the beam measurementconfiguration information and the DRX configuration information from theeNB.

The controller 2 l-40 controls the UE to start beam measurement and DRXoperation immediately upon receipt of the configuration information orat a predetermined time point after the receipt of the configurationinformation. The controller 2 l-40 may perform beam measurementperiodically to check for change of the best beam pair.

The controller 2 l-40 may control the UE to report the change of thebest beam pair to the eNB, suspend the currently running DRX operation,and maintain the Active Time. Here, the controller 2 l-40 may controlthe UE to send the eNB the information on the best beam. The controller2 l-40 may also control the UE to transmit to the eNB the informationindicating that the best beam pair has been changed.

The controller 2 l-40 maintains the Active Time during a predeterminedtime period or until a predetermined even occurs and then resumes theDRX operation immediately or at a predetermined time point. As describedabove, the predetermined event may be receiving the new beamconfiguration information from the eNB. The controller 2 l-40 maycontrol the UE to receive the information on the new best beam pair fromthe eNB and resume the DRX operation.

The information on the predetermined time period concerning the resumeof the DRX operation may be included in the DRX configurationinformation, and the controller 2 l-40 may control UE to resume the DRXoperation after the predetermined time period expires.

FIG. 2M illustrates a configuration of an eNB according to the presentdisclosure.

As shown in FIG. 2M, the eNB includes an RF processing unit 2 m-10, abaseband processing unit 2 m-20, a backhaul communication unit 2 m-30, amemory 2 m-40, and a controller 2 m-50. In the present disclosure, thecontroller 2 k-50 may be interchangeably referred to as a circuit, anapplication-specific integrated circuit, and at least one processor andthe controller may be coupled with the transceiver.

The RF processing unit 2 m-10 may perform the same function as the RFprocessing unit 1 k-10 of FIG. 1K and thus detailed description thereofis omitted herein.

The baseband processing unit 2 m-20 may perform the same functions asthe baseband processing unit 1 k-20 of FIG. 1K and thus detaileddescription thereof is omitted herein.

The baseband processing unit 2 m-20 and the RF processing unit 2 m-10are involved in signal transmission and reception. For this reason, thebaseband processing unit 2 m-20 and the RF processing unit 2 m-10 may bereferred to as a transmit unit, a receive unit, a transceiver, or acommunication unit.

The backhaul communication unit 2 m-30 may perform the same functions ofthe backhaul communication unit 1 k-30 of FIG. 1K and thus detaileddescription thereof is omitted herein.

The memory 2 m-40 may perform the same function as the memory 1 k-40 ofFIG. 1K and thus detailed description thereof is omitted herein.

The controller 2 m-50 controls overall operations of the primary eNB.For example, the controller 2 m-50 transmits/receives signals by meansof the baseband processing unit 2 m-20 and the RF processing unit 2m-10. The controller 2 m-50 writes and reads data to and from the memory2 m-40. For this purpose, the controller 2 m-50 may include at least oneprocessor and the controller may be coupled with the transceiver.

In detail, the controller 2 m-50 controls the eNB to transmit DRXconfiguration information to the UE. The controller 2 m-50 may calculatethe best DRX parameters (DRX cycle and drx-InactivityTimer) values basedon various information such as DRB characteristics, traffic pattern,buffer status, and frame structure.

The controller 2 m-50 may control the eNB to transmit a DRX MAC CE (orDRX configuration information) to the UE. This MAC CE may include theconfiguration information for updating DRX parameters. This MAC CE mayinclude a multiple of at least one of the DRX cycle and DRX-relatedtimer values or new DRX cycle and drx-InactivityTimer values.

The controller 2 m-50 may control the eNB to transmit a MAC CE to the UEto change the DRX configuration information or initializes the DRXparameters to the default DRX parameter values.

It may be considered for the controller 2 m-50 controls the eNB totransmit the DRX configuration information including two or more timervalues for updating the DRX-related timer and instruct the UE to selectand use one of the timer values by transmitting a MAC CE.

According to another embodiment of the present disclosure, thecontroller 2 m-50 may check the beam-based function capability of the UEbased on the UE capability information included in an RRC messagetransmitted by the UE. The controller 2 m-50 may notify the UE of itsbeam-based function supportability using the system information itbroadcasts.

The controller 2 m-50 may control the eNB to transmit at least one ofthe beam measurement configuration information and the DRX configurationinformation. The controller 2 m-50 may control the eNB to transmit a MACCE for triggering a DRX operation of the UE. However, the MAC CE may notbe transmitted if the information on the DRX start time point isincluded in the DRX configuration information or predetermined.

If the best beam pair is changed, the controller 2 m-50 may control theeNB to receive the information on the best beam. The controller 2 m-50may also control the eNB to receive the information indicating that thebest beam pair has been changed.

The controller 2 m-50 may control the eNB to transmit new beamconfiguration information indicating the new best beam pair to the UE.

Third Embodiment

FIG. 3A illustrates architecture of an LTE system. The detaileddescription of the LTE system architecture has been made already withreference to FIG. 1A and thus is omitted herein.

FIG. 3B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system.

In reference to FIG. 3B, the protocol stack of the interface between theUE and the eNB in the LTE system includes a PDCP layer denoted byreference numbers 3 b-05 and 3 b-40, an RLC layer denoted by referencenumbers 3 b-10 and 3 b-35, a MAC layer denoted by reference numbers 3b-15 and 3 b-30, and a PHY layer denoted by reference numbers 3 b-20 and3 b-25.

The PDCP layer denoted by reference numbers 3 b-05 and 3 b-40 takescharge of compressing/decompressing an IP header, and the RLC layerdenoted by reference numbers 3 b-10 and 3 b-35 takes charge ofsegmenting a PDCP PDU into segments of appropriate size.

The MAC layer denoted by reference number 3 b-15 and 3 b-30 allows forconnection of multiple RLC entities established for one UE and takescharge of multiplexing RLC PDUs from the RLC layer into a MAC PDU anddemultiplexing a MAC PDU into RLC PDUs.

The PHY layer denoted by reference numbers 3 b-20 and 3 b-25 takescharge of channel-coding and modulation on higher layer data to generateand transmit OFDM symbols over a radio channel, and demodulating andchannel-decoding on OFDM symbols received over the radio channel, thedecoded data being delivered to the higher layers. The PHY layer denotedby reference numbers 220 and 225 uses Hybrid Automatic Repeat Request(HARQ) for additional error correction by transmitting 1-bit informationindicating positive or negative acknowledgement about data packet, theacknowledgement being transmitted from the receiver to the transmitter.The 1-bit information is referred to as acknowledgement/negativeacknowledgement (ACK/NACK). The downlink HARQ ACK/NACK corresponding toan uplink transmission may be transmitted in Physical Hybrid-ARQIndicator Channel (PHICH), and the uplink HARQ ACK/NACK corresponding toa downlink transmission may be transmitted in Physical Uplink ControlChannel (PUCCH) or Physical Uplink Shared Channel (PUSCH).

Typically, HARQ schemes are categorized into two types: asynchronousHARQ and synchronous HARQ. The asynchronous HARQ is characterized inthat the retransmission timing is not fixed, while the synchronous HARQis characterized in the retransmission time is fixed (e.g., 8 ms). Forone UE, multiple transmissions may be performed simultaneously indownlink and uplink, and the transmissions are identified withrespective HARQ process identifiers.

Since the retransmission timing is not fixed in the asynchronous HARQ,the eNB send the UE the HARQ process identifier (ID) and information onwhether the current transmission is a new transmission or aretransmission through a Physical Downlink Control Channel (PDCCH). Indetail, the HARQ process ID is included in a HARQ Process ID field ofthe PDCCH and the information on whether the current transmission is anew transmission or a retransmission is indicated by a New DataIndicator (NDI) bit of the PDCCH, the NDI bit being toggled forretransmission or not toggled for new transmission relative to theprevious transmission. Accordingly, the UE checks for the detail of thecorresponding transmission based on the resource allocation informationincluded in the PDCCH transmitted by the eNB to receive downlink datathrough a Physical Downlink Shared Channel (PDSCH) and transmit uplinkdata through a Physical Uplink Shared Channel (PUSCH).

Although now shown in the drawing, a Radio Resource Control (RRC) layerresides above the PDCP layer in both the UE and the eNB, which mayexchange connection and measurement-related RRC control messages.

FIG. 3C illustrates a network environment to which the presentdisclosure is applied.

In FIG. 3C, a cell is managed by a Central Unit (CU) 3 c-01, and one CUcontrols one or more Distributed Units (DUs) 3 c-11, 3 c-13, 3 c-15, 3c-17, 3 c-21, 3 c-23, 3 c-25, 3 c-27, 3 c-29, 3 c-31, 3 c-33, and 3c-35. A cell may have a very large coverage 3 c-61, and this means thatthe paging area is too large to transmit a paging message efficiently towake up a terminal in the idle mode when data destined for the terminalarrives.

In the present disclosure, a cell is divided into a plurality of pagingareas 3 c-51, 3 c-53, and 3 c-55 such that the network broadcasts thepaging message within the paging area where the target terminal islocated.

For example, if a terminal is located close to a transmission/receptionantenna (or transmission/reception port; TRP) 3 c-11 or receivesdifferent TRP identifiers (TRP IDs) from multiple TRPs, it reports thisto the network, which broadcasts the paging message within thecorresponding paging area, i.e., paging area 1 3 c-51.

FIG. 3D illustrates a proposed paging procedure between a terminal and anetwork according to the present disclosure.

In exemplary situation of FIG. 3D, it is assumed that the terminal 3d-01 is in the idle mode and close to the TRP 1 3 d-03. Accordingly, theterminal 3 d-01 receives a TRP ID or a Beam Identifier (BI)transmittedby the TRP 1 3 d-03 at step 3 d-11.

The terminal 3 d-01 may receive a system information block broadcast bythe 5G NB 1 (or CU) 3 d-07 at step 3 d-13. The system information blockis equivalent to SystemInformationBlock of LTE for use in broadcastingcell-specific information to the terminals within a cell. The systeminformation block includes paging area identifiers (corresponding toTracking Area Code in LTE) and a set of TRP IDs (or BIs) for the TRPsforming a paging area.

The terminal 3 d-01 may identify the paging area (e.g., paging areas 3c-51, 3 c-53, and 3 c-55 if FIG. 3C) based on the system informationblock. In the exemplary situation of FIG. 3C, the 5G NB may broadcastthe information on the TRPs belonging to the respective paging areas 3c-51, 3 c-53, and 3 c-55; if the terminal is located in the paging area1 3 c-51, the 5G NB may inform that the paging area 1 3 c-51 is formedwith the TRPs 3 c-11, 3 c-13, 3 c-15, and 3 c-17.

After receiving the system information block, if its location has notbeen registered with the network for receiving a paging message, theterminal 3 d-01 transmits a paging area update message to register itslocation with the network at step 3 d-15. In this exemplary situation,it is assumed that the terminal is located close to the TRP 3 c-17 asshown in FIG. 3C for convenience of explanation.

The paging area update message may be transmitted to the 5G NB 3 d-07and an MME 3 d-09 (equivalent to MME in LTE). Accordingly, it may benecessary for the terminal to register it location with the 5g NB andMME, which broadcast a paging message to notify the terminal of thearrival of packets destined therefor. If a packet destined to theterminal arrives, the MME 3 d-09 may send a paging message to the 5G NB1 3 d-07 at step 3 d-21, the 5G NB 1 3 d-07 may send the paging messageto the TRP 1 3 d-03 belonging to the corresponding paging area at step 3d-23, and then the TRP 1 3 d-03 broadcasts the paging messages at step 3d-25.

In the exemplary situation of FIG. 3D, the terminal 3 d-01 moves fromone paging area to another at step 3 d-29. In the following description,it is assumed that the terminal moves close to the TRP 3 c-23 as shownin FIG. 3C for convenience of explanation.

The terminal 3 d-01 receives a TRP ID from the TRP 2 3 d-05 belonging tothe new paging area at step 3 d-31. The terminal 3 d-01 may be awarethat it has moved close to the TRP 2 3 d-05 belonging to the new pagingarea based on the TRP ID received at step 3 d-31. Next, the terminal 3d-01 transmits a paging area update message to register its currentlocation with the network at step 3 d-35.

In this case, since the terminal 3 d-01 has changed the paging areawithin a cell, it registers its location with the 5G NB 1 3 d-07 at step3 d-31 without transmitting any signal to the MME 3 d-09. That is, theterminal 3 d-01 may transmit the paging update message to the 5G NB 1 3d-07.

In the case that the terminal 3 d-01 moves within the same cell linkthis, the MME 3 d-09 may transmit the pacing message to the same 5G NB,i.e., 5G NB 1 3 d-07 at step 3 d-41. However, since the UE has moved toa new paging area, the 5G NB 1 3 d-07 sends the paging message to theTRP 2 3 d-05 belonging to the new paging area at step 3 d-43, and theTRP 2 3 d-05 broadcasts the paging message at step 3 d-45.

In LTE, however, if a UE in the light connected mode moves from onepaging area to another, it transitions to the connected mode to transmita paging update message. Here, it may be expressed that the UE in thelight connected mode is in the inactive state in which the UE isconnected to the eNB in the state that the eNB has not deleted the UE(e.g., UE context). However, this may cause a problem in that the UEtransitions to the connected mode unnecessarily even though there is nodata to transmit or receive.

Accordingly, the UE in the light connected mode may transition back tothe inactive state rather than the connected mode even when it isnecessary to transmit the paging area update message.

The information indicating the change of the paging area may be includedin, but not limited to, a paging area update message or a resume requestmessage, and the name of the message transmitted from the UE to the eNBmay be changed.

In the exemplary situation of FIG. 3D, the terminal 3 d-01 moves toanother 5G NB, i.e., 5G NB 2 3 d-08 having other paging areas at step 3d-49.

After having moved to the 5G NB 2 3 d-08, the terminal 2 d-01 mayreceive a system information block from the 5G NB 2 3 d-08 at step 3d-53. As described above, the system information block may includepaging area identifiers and a set of TRP IDs (or BIs) of the TRPsforming a paging area.

The terminal 3 d-01 may make a paging area update determination forreceiving a paging message to a new cell based on the 5G NB/cellidentifier and paging area identifier included in the system informationblock. The terminal 3 d-01 may transmit a paging area update message tothe 5G NB 2 3 d-08 and the MME 3 d-09 to register its location therewithat step 3 d-55.

Afterward, if a packet destined for the terminal 3 d-01 arrives at thenetwork, the paging message can be broadcast in the correct paging area.

FIG. 3E illustrates a paging area update procedure of a terminalaccording to the present disclosure.

A terminal may receive a cell-specific information and a systeminformation block from a TRP of a 5G NB at step 3 e-03. The cellspecific information may include at least one of a cell identifier and aTRP ID (or BI).

The system information block is equivalent to SystemInformationBlock ofLTE for use in broadcasting cell-specific information to the terminalswithin a cell. The system information block includes paging areaidentifiers (corresponding to Tracking Area Code in LTE) and a set ofTRP IDs (or BIs) for the TRPs forming a paging area.

If the above information is received, the terminal determines at step 3e-05 whether it has initially registered its location with the networkor the paging area has been changed.

If the paging area has been changed, the terminal may determine whetherthe paging area change is an intra-5G NB/cell paging area change or aninter-5G NB/cell paging area change at step 3 e-07. In other words, theterminal determines whether the paging area is changed within a cell orto another cell.

If it is determined that the terminal has initially registered itslocation or the paging area change is the inter-5G NB/cell paging areachange, the terminal transmits a paging area update message to theserving 5G ND and the MME (e.g., MME 3 d-09 of FIG. 3D) at step 3 e-09.

Otherwise, if it is determined that paging area change is the intra-5GNB/cell paging area change, the terminal transmits the paging areaupdate message to only the 5G NB at step 3 e-11.

FIG. 3F illustrates a configuration of a terminal according to thepresent disclosure.

In reference to FIG. 3F, the terminal includes an RF processing unit 3f-10, a baseband processing unit 3 f-20, a memory 3 f-30, and acontroller 3 f-40. In the present invention, the controller 2 l-40 maybe interchangeably referred to as a circuit, an application-specificintegrated circuit, and at least one processor and the controller may becoupled with the transceiver.

The RF processing unit 3 f-10 may perform the same function as the RFprocessing unit 1 j-10 of FIG. 1J and thus detailed description thereofis omitted herein.

The baseband processing unit 3 f-20 may perform the same functions asthe baseband processing unit 1 j-20 of FIG. 1J and thus detaileddescription thereof is omitted herein.

The baseband processing unit 3 f-20 and the RF processing unit 3 f-10are involved in signal transmission and reception as described above.Accordingly, the baseband processing unit 3 f-20 and the RF processingunit 3 f-10 may be referred to as a transmit unit, a receive unit, atransceiver, or a communication unit. The detailed description thereofhas been described with reference to FIG. 1J and thus omitted herein.The memory 3 f-30 may be identical in functionality with the memory 1j-30 as described with reference to FIG. 1J and thus detaileddescription thereof is omitted herein.

The controller 3 f-40 controls overall operations of the UE. Forexample, the controller 3 f-40 transmits/receives signals by means ofthe baseband processing unit 3 f-20 and the RF processing unit 3 f-10.The controller 3 f-40 writes and reads data to and from the memory 3f-40. For this purpose, the controller 3 f-40 may include at least oneprocessor. For example, the controller 3 f-40 may include aCommunication Processor (CP) for controlling communication and anApplication Processor (AP) for controlling higher layer applicationprograms. According to an embodiment of the present disclosure, thecontroller 3 f-40 includes a multi-connectivity processing unit 3 f-42for the operation in the multi-connectivity mode. For example, thecontroller 3 f-40 may control the terminal to perform the operations ofthe procedure of FIG. 3E.

According to an embodiment of the present disclosure, the controller 3f-40 makes a paging update determination based on the system informationblock, cell identifiers and TRP IDs received from the 5G NB andtransmits the paging area update message to both the 5G NB and MME oronly the 5G NB as described with reference to FIG. 3E.

Fourth Embodiment

FIG. 4A illustrates architecture of an LTE system to which the presentdisclosure is applied. The detailed description of the LTE systemarchitecture has been made already with reference to FIG. 1A and thus isomitted herein.

FIG. 4B illustrates a protocol stack of an interface between a terminaland an eNB in the LTE system. The detailed description of the protocolstack has been made already with reference to FIGS. 2B and 3B and thusis omitted herein.

FIG. 4C illustrates signal flows between a terminal and a base stationin a signal transmission method proposed in the present disclosure.

Although FIG. 4C is directed to the uplink data transmission of theterminal (i.e., data transmission from a terminal to a base station), itmay also be possible to apply the method to a downlink datatransmission.

In the transmission method of the present disclosure, the terminal 4c-01 may transmit its capability information to the base station 4 c-03at step 4 c-11. The capability information may include UECapabilitycarried in an RRC message. The capability information may include theinformation indicating whether the terminal supports the method proposedin the present disclosure. The present disclosure proposes a redundantdata transmission over multiple resources for providing a URLLC serviceto be described later. Accordingly, the capability information mayinclude the information indicating whether the terminal supports theredundant data transmission over multiple resources. The capabilityinformation may also include the information indicating whether theterminal supports the URLLC service.

The base station 4 c-03 may transmit configuration information to theterminal 4 c-01 at step 4 c-13. The base station 4 c-03 may transmit theconfiguration information for allowing the use of the transmissionmethod proposed in the present disclosure, and the configurationinformation may include URLLC grant configuration information. Theconfiguration information may be transmitted in an RRC message to theterminal 4 c-01.

The message transmitted from the base station 4 c-03 to the terminal 4c-01 may include at least one of resource allocation periodicity (grantperiodicity), physical resource position and transmission scheme(Modulation and Coding Scheme (MCS)), and information on carriers foruse in transmission. The grant periodicity is the information indicatingthe indicating initial transmission resource for semi-persistentresource allocation to be described later and, if this information isincluded, it is not necessary for the base station to transmit theresource allocation message for every transmission (e.g., datatransmission at step 4 c-23).

If the configuration message is received, the terminal 4 c-01 may notifythe base station of the use of the corresponding transmission method forthe uplink transmission of the terminal (or the downlink transmission ofthe base station) at step 4 c-15. The configuration message may be a MAClayer message or an RRC layer message for use in LTE. This message maybe referred to as URLLC preference message and, if this message isreceived, the base station may allocate resources according to themethod proposed in the present disclosure.

Upon receipt of the configuration message or a notification message, thebase station 4 c-03 may start resource allocation according to themethod proposed in the present disclosure. The correspondingtransmission method is characterized in that the UE 4 c-01 transmitsdata at steps 4 c-19 and 4 c-23 according to the resource allocationmessage (URLLC resource grant) which the eNB 4 c-03 transmits at steps 4c-17 and 4 c-21; the detailed description thereof is made with referenceto FIG. 4D.

The resource allocation message may include at least one of physicalresource position and transmission scheme (Modulation and Coding Scheme(MCS)), information on the carriers for use in transmission (e.g., inthe form of a bitmap), transmission pattern. For example, if theterminal uses 4 carriers for data transmission among the total 10component carriers configured by the base station, the message mayinclude the information on the 4 carrier frequencies (in the format of abitmap). The physical resource position and transmission scheme (MCS)information may be transmitted per carrier frequency or as a commoninformation for 4 carrier frequencies. If multiple transmission patternsare configured as to be described later, the resource allocation messagemay include the pattern information.

However, the base station may include the resource allocationinformation as a part of the RRC configuration information. The basestation may transmit part of the resource allocation information(physical resource position, transmission method, information on thecarriers for use in transmission, and transmission pattern) through anRRC message and the remaining part through a resource allocation messagetransmitted on PDCCH. For example, the base station may transmit to theterminal the transmission pattern information through an RRC message andnotify the terminal of the resource position for data transmission usinga resource allocation message in the PDCCH. The base station maytransmit the above-described information through one of the RRC messageand the resource allocation message on PDCCH. For example, if theresource allocation information is carried in the RRC message, theterminal may transmit data according to the predetermined transmissionpattern and physical resource position. If the base station transmitsthe resource allocation information using the resource allocationmessage, the terminal may transmit data based on the resourcedynamically allocated using the resource allocation information.

In correspondence to the notification message, the base station 4 c-03may transmit a message indicating that the use of the configuredtransmission method is stopped at step 4 c-25.

FIGS. 4DA, 4DB, and 4DC illustrate a transmission method according tothe present disclosure.

Although the drawings are directed to uplink transmission of a UE, thesame method may be applied to downlink transmission.

In FIGS. 4DA to 4DC, the horizontal axis time, and the vertical axisdenotes frequency; the drawings depict the concept of resourceallocation to a terminal in the time domain for data transmission of theterminal. Reference number 4 d-01 denotes the resources allocated by abase station and is equivalent to PDCCH in LTE. The base stationallocates the resources 4 d-01 to the terminal, and the resource 4 d-01may include at least one of physical resource position and modulationscheme (MCS) for data transmission, carriers for use in datatransmission (e.g., in the form of a bitmap), and transmission pattern.

The terminal transmits data to the base station based on the aboveinformation in a pattern as denoted by reference numbers 4 d-11, 4 d-13,4 d-15, and 4 d-17. Reference numbers 4 d-11, 4 d-13, 4 d-15, and 4 d-17denote data being transmitted through PUSCH in LTE, i.e., RedundancyVersions (RVs) of the same data but encoded in different channel codingschemes on the physical layer. A receiver (base station in the drawings)combines the RV(s) accumulatively to increase the successful datareception probability.

A receiver (base station in the drawings) receives the PUSCH and thenacknowledges whether the data are received successively through apredetermined channel. Reference number 4 d-03 denotes this channelwhich corresponds to Physical Hybrid ARQ Indicator Channel (PHICH) inLTE.

The drawings depict scenarios of transmitting data over 4 ComponentCarriers (CCs) as denoted by reference numbers 4 d-21, 4 d-23, 4 d-25,and 4 d-27.

FIG. 4DA illustrates a transmission method proposed in the presentdisclosure.

Parts (4 d-A) and (4 d-B) of FIG. 4DA show scenarios in which a terminaltransmit data continuously but hopping among the CCs in the resourcesallocated by the base station.

That is, the terminal is allocated resources through the PDCCH 4 d-01and transmits data continuously but hopping among the CCs according to apredetermined pattern or a pattern configured by the base station.

Part (4 d-A) of FIG. 4DA exemplifies a case where the same RVs areconsecutively transmitted, and part (4 d-B) of FIG. 4DA exemplifies acase where the different RVs are consecutively transmitted. As shown inthe drawing, the frequency resource positions are fixed on each CC andthis contributes to reduction of resource allocation overhead.

As described above, the base station may notify the terminal of thetransmission pattern (or resource pattern) as shown in part (4 d-A) or(4 d-B) of FIG. 4DA using an RRC message or resource allocationinformation conveyed on PDCCH such that the terminal transmits data inthe transmission pattern. The base station may also transmit a bitmapindicating the transmission position on the respective CCs and RVmapping scheme to the terminal using an RRC message or the resourceallocation information conveyed on PDCCH.

For example, the base station may notify the UE of the transmissionpattern as shown in part (4 d-A) or (4 d-B) of FIG. 4DA and the RVmapping scheme in an RRC message and of the data transmission startposition of the terminal in the resource allocation information conveyedon PDCCH.

The above method for transmitting resource allocation information to theterminal may be applied throughout the present disclosure including theembodiments of FIGS. 4B and 4C.

Afterward, the receiver (base station in the embodiment) may transmit anacknowledgement signal 4 d-03 corresponding to the data. The basestation may transmit the acknowledgement per every transmissionincluding the initial transmission or corresponding to the last one ofthe consecutive data transmissions.

FIG. 4DB illustrates a transmission method proposed in the presentdisclosure.

Parts (4 d-C) and (4 d-D) of FIG. 4DB show scenarios in which a terminaltransmit the same data over multiple CCs simultaneously in the resourcesallocated by the base station.

Part (4 d-C) of FIG. 4DB exemplifies a case where the same RV of data istransmitted over the multiple CCs simultaneously, and Part (4 d-B) ofFIG. 4DB exemplifies a case where the different RVs are transmitted overthe multiple CCs simultaneously. As shown in the drawing, the frequencyresource positions are fixed on each CC and this contributes toreduction of resource allocation overhead.

Afterward, the receiver (base station in this embodiment) may transmitan acknowledgement 4 d-03 corresponding to the data.

FIG. 4DC illustrates a transmission method proposed in the presentdisclosure.

Parts (4 d-E) and (4 cd-F) of FIG. 4DC show scenarios in which aterminal transmit the same data over multiple CCs simultaneously in theresources allocated by the base station.

Part (4 d-E) of FIG. 4DC exemplifies a case where one RV of the data istransmitted over the multiple CCs simultaneously and another RV istransmitted over the multiple CCs simultaneously, and Part (4 d-F) ofFIG. 4DC exemplifies a case where different RVs are transmitted over themultiple CCs simultaneously in a consecutive manner. As shown in thedrawing, the frequency resource positions are fixed on each CC and thiscontributes to reduction of resource allocation overhead.

Afterward, the receiver (base station in this embodiment) may transmitan acknowledgement 4 d-03 corresponding to the data. The base stationmay transmit the acknowledgement per every transmission including theinitial transmission or corresponding to the last one of the consecutivedata transmissions.

FIG. 4EA is a flowchart illustrating a terminal operation according tothe present disclosure.

The terminal may transmit capability information to the base station atstep 4 e-03. The capability information may include UECapability carriedin an RRC message. The capability information may include theinformation indicating whether it supports the method proposed in thepresent disclosure. As described above, the capability information mayinclude the information indicating whether the terminal supports theredundant data transmission over multiple resources. The capabilityinformation may also include the information on whether the terminalsupports the URLLC service. That is, the terminal transmits to the basestation the information indicating whether it supports the transmissionmethod proposed in the present disclosure at step 4 e-03.

The base station may configure the transmission method (or transmissionscheme or transmission mode) proposed in the present disclosure for theterminal based on the above information.

The terminal receives a configuration message from the base station atstep 4 e-05. The configuration message may include at least one of aresource allocation period, physical resource position and transmissionscheme (MCS), and information on carriers for use in transmission (e.g.,in the form of a bitmap). The configuration information may betransmitted in an RRC message to the terminal.

The terminal may apply the proposed transmission method immediately uponreceipt of the configuration message or transmit a predetermined messageto the base station to notify the base station that it wants to use thecorresponding transmission method at the uplink transmission timing atstep 4 e-07. This message may be equivalent to a MAC layer or an RRClayer message in LTE. In the case of applying the transmission methodupon receipt of the configuration message, the terminal may transmitdata based on the resource allocation information included in theconfiguration message. In this case, step 4 e-07 may be omitted.

In or der to notify the base station of the interest in use of theproposed transmission method, the terminal may transmit an URLLCpreference message to the base station.

If the configuration message or notification message is received, thebase station may configure the proposed transmission method for theterminal using a resource allocation message (corresponding to a messageconveyed on PDCCH in LTE).

That is, the base station transmits to the terminal the resourceallocation message including a predetermined indicator indicating one oftransmission method 1 and transmission method 2 proposed in the presentdisclosure.

The terminal may receive a resource allocation message and determine atstep 4 e-09 whether to use transmission method 1 or transmission method2 based on the information included in the resource allocation message.

If the base station has instructed to use transmission method 1, theterminal transmits data once based on the designated resourceinformation in the resource allocation message at step 4 e-11.

If the base station has instructed to use transmission method 2, theterminal may transmit data using a predetermined method or a methodindicated in the information received at step 4 e-05 on the basis of theinformation included in the resource allocation message. The terminalmay also transmit data based on the resource allocation informationincluding in the configuration information received at step 4 e-05 andthe information included in the resource allocation information.

For example, the terminal may transmit the data over multiple resourcesredundantly (repeatedly or with duplication) based on the transmissionpattern indicated in the information received at step 4 e-05 and thedata transmission timing information included in the resource allocationmessage.

The terminal may transmit data according to one of the transmissionmethods exemplified in FIGS. 4DA to 4DC at step 4 e-13. That is, theterminal may transmit data redundantly over multiple resources for theURLLC service. In other words, the terminal may transmit same data inmultiple resources. The redundant data transmission over multipleresources may be performed with one of the transmission patternsdepicted in FIGS. 4DA to 4DC. The pattern information may be carried inan RRC configuration information or a resource allocation messageconveyed on PDCCH.

In order to apply one of the patterns exemplified in FIGS. 4DA to 4DC,the receiver may use one or more buffers for receiving data. Forexample, the receiver may receive data in such a way of buffering databeing received over multiple component carriers in a signal buffer or incarrier-specific buffers (for low implementation complexity) andcombining the buffered data and, if the data is received successfully,it may acknowledge the successful receipt to the transmitter (basestation in this embodiment).

The terminal may determine at step 4 e-15 whether to stop using theconfigured uplink transmission method. If it is determined to stop usingthe configured uplink transmission method, the terminal transmits to thebase station a message indicating that the configured transmissionmethod is terminated at step 4 e-17.

FIG. 4EB is a flowchart illustrating a base station operation accordingto the present disclosure.

The base station may receive capability information from the terminal atstep 4 e-51. The capability information may include UECapability carriedin an RRC message, and the terminal may include information indicatingwhether it supports the transmission method proposed in the presentdisclosure in the capability information. The transmission methodproposed in the present disclosure may be the redundant datatransmission over multiple resources.

The base station may instruct the terminal to activate the proposedtransmission method based on the capability information.

The base station transmits a configuration message to the terminal atstep 4 e-53. may include at least one of a resource allocation period,physical resource position and transmission scheme (MCS), andinformation on carriers for use in transmission (e.g., in the form of abitmap). The configuration information may be transmitted in an RRCmessage to the terminal.

The base station may receive a predetermined message at an uplinktransmission timing of the terminal at step 4 e-55 so as to check thatthe terminal wants to use the configured transmission method. Theterminal may start transmission immediately upon receipt of theconfiguration message and, in this case, step 4 e-55 may be omitted.

The base station may transmit a resource allocation message to theterminal at step 4 e-57. The base station may instruct the terminal toUE the proposed transmission method using the resource allocationmessage.

The base station may receive data in the resources allocated to theterminal at step 4 e-59.

Here, the base station may receive data transmitted in one of themethods exemplified in FIGS. 4DA to 4DC. That is, the base station mayreceive the data transmitted in the transmission method of redundantdata transmission over multiple resources. The terminal performs theredundant data transmission over multiple resources in one of thetransmission patterns depicted in FIGS. 4DA to 4DC. The patterninformation may be carried in an RRC configuration information or aresource allocation message conveyed on PDCCH.

FIG. 4F illustrates a configuration of a terminal according to anembodiment of the present disclosure.

In reference to FIG. 4F, the terminal includes an RF processing unit 4f-10, a baseband processing unit 4 f-20, a memory 4 f-30, and acontroller 4 f-40. In the present invention, the controller 2 l-40 maybe interchangeably referred to as a circuit, an application-specificintegrated circuit, and at least one processor and the controller may becoupled with the transceiver.

The RF processing unit 4 f-10 may perform the same function as the RFprocessing unit 1 j-10 of FIG. 1J and thus detailed description thereofis omitted herein.

The baseband processing unit 4 f-20 may perform the same functions asthe baseband processing unit 1 j-20 of FIG. 1J and thus detaileddescription thereof is omitted herein.

The baseband processing unit 4 f-20 and the RF processing unit 4 f-10are involved in signal transmission and reception as described above.Accordingly, the baseband processing unit 4 f-20 and the RF processingunit 4 f-10 may be referred to as a transmit unit, a receive unit, atransceiver, or a communication unit. The detailed description thereofhas been described with reference to FIG. 1J and thus omitted herein.The memory 4 f-30 may be identical in functionality with the memory 1j-30 as described with reference to FIG. 1J and thus detaileddescription thereof is omitted herein. The controller 4 f-40 controlsoverall operations of the UE. For example, the controller 4 f-40transmits/receives signals by means of the baseband processing unit 4f-20 and the RF processing unit 4 f-10. The controller 4 f-40 writes andreads data to and from the memory 4 f-40. For this purpose, thecontroller 4 f-40 may include at least one processor. For example, thecontroller 4 f-40 may include a Communication Processor (CP) forcontrolling communication and an Application Processor (AP) forcontrolling higher layer application programs. According to anembodiment of the present disclosure, the controller 4 f-40 includes amulti-connectivity unit 4 f-42 for the operation in themulti-connectivity mode. For example, the controller 4 f-40 may controlthe terminal to perform the operations in the procedure of FIG. 4EA.

According to an embodiment of the present disclosure, the controller 4f-40 controls the terminal to transmit data in the proposed transmissionmethod based on the configuration information received from the basestation.

FIG. 4G illustrates a configuration of a base station according to anembodiment of the present disclosure.

As shown in FIG. 4G, the base station includes an RF processing unit 4g-10, a baseband processing unit 4 g-20, a backhaul communication unit 4g-30, a memory 4 g-40, and a controller 4 g-50. In the presentdisclosure, the controller 4 g-50 may be interchangeably referred to asa circuit, an application-specific integrated circuit, and at least oneprocessor and the controller may be coupled with the transceiver.

The RF processing unit 4 g-10 may perform the same function as the RFprocessing unit 1 k-10 of FIG. 1K and thus detailed description thereofis omitted herein.

The baseband processing unit 4 g-20 may perform the same functions asthe baseband processing unit 1 k-20 of FIG. 1K and thus detaileddescription thereof is omitted herein.

The baseband processing unit 4 g-20 and the RF processing unit 4 g-10are involved in signal transmission and reception. For this reason, thebaseband processing unit 4 g-20 and the RF processing unit 4 g-10 may bereferred to as a transmit unit, a receive unit, a transceiver, or acommunication unit.

The backhaul communication unit 4 g-30 may perform the same functions ofthe backhaul communicating unit 1 k-30 of FIG. 1K and thus detaileddescription thereof is omitted herein. The memory 4 g-40 may perform thesame function as the memory 1 k-40 of FIG. 1K and thus detaileddescription thereof is omitted herein.

The controller 4 g-50 controls overall operations of the base station.For example, the controller 4 g-50 transmits/receives signals by meansof the baseband processing unit 4 g-20 and the RF processing unit 4g-10. The controller 4 g-50 writes and reads data to and from the memory4 g-40. For this purpose, the controller 4 g-50 may include at least oneprocessor and the controller may be coupled with the transceiver.

According to an embodiment of the present disclosure, the controller 4g-50 determines whether the terminal supports the proposed transmissionmethod and, if so, configures the transmission for the terminal. Thatis, the base station may allocate resources to the terminal for use ofthe proposed transmission method and instruct the terminal to use theproposed transmission method using the resource allocation message. Thedetailed description thereof has been made above and thus is omittedherein. The baseband processing unit 4 g-20 manage one or more buffersfor receiving data and acknowledges whether the data is receivedsuccessfully.

Fifth Embodiment

FIG. 5A illustrates architecture of an LTE system.

The detailed description of the LTE system architecture has been madealready with reference to FIG. 1A and thus is omitted herein.

FIG. 5B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system.

The detailed description of the protocol stack has been made alreadywith reference to FIGS. 2B and 3B and thus is omitted herein.

FIG. 5C illustrates a handover procedure in a legacy LTE system.

The UE 5 c-01 in the connected mode transmits a measurement report to asource eNB 5 c-02 at step 5 c-05 periodically or when a predeterminedevent occurs.

The source eNB 5 c-02 determines whether to trigger handover of the UE 5c-01 to a neighboring eNB. Typically, a handover decision is made for aUE in the connected mode to hand over the control from one eNB toanother.

If the source eNB has made the handover decision for the UE 5 c-01, ittransmits a handover (HO) request message to another eNB, i.e., targeteNB 5 c-03, to serve the UE 5 c-01 at step 5 c-10.

If the target eNB 5 c-03 accepts the handover request, it transmits a HOrequest acknowledgement (Ack) to the source eNB 5 c-02 at step 5 c-15.

If the HO request Ack is received, the source eNB 5 c-02 transmits an HOcommand to the UE 5 c-01 at step 5 c-20. The HO command may be carriedin the RRC Connection Reconfiguration message transmitted from thesource eNB 5 c-02 to the UE 5 c-01. If the RRC ConnectionReconfiguration message is received, the UE 5 c-01 stops datacommunication with the source eNB 5 c-02 and starts a T304 timer. TheT304 timer is used for the UE 5 c-01 to restore the previous settingsand transition to the RRC idle state when the UE 5 c-01 fails handoverto the target eNB 5 c-03 in a predetermined time duration.

The source eNB 5 c-02 transmits Sequence Number (SN) status informationof uplink/downlink data to the target eNB 5 c-03 at step 5 c-30 and, ifdownlink data exists, forwards the downlink data to the target eNB 5c-03 at step 5 c-35.

Afterward, the UE 5 c-01 attempts random access to the target eNB 5 c-03at step 5 c-40. The random access is attempted to notify the target eNB5 c-03 of the handover thereto and achieve uplink synchronization. Forthe random-access attempt, the UE 5 c-01 transmits to the target eNB 5c-03 a preamble corresponding to a preamble ID provided by the sourceeNB 5 c-02 or selected randomly.

After a predetermined number of subframes since the preambletransmission, the UE 5 c-01 monitors for a Random Access Response (RAR).The monitoring time period is referred to as RAR window. If the RAR isreceived in a predetermined time period at step 5 c-45, the UE 5 c-01transits to the target eNB 5 c-03 an HO complete message in the RRCConnection Reconfiguration Complete(RRCConnectionReconfigurationComplete) message at step 5 c-55. If theRAR is received successfully, the UE 5 c-01 stops the T304 timer at step5 c-50.

The target eNB 5 c-03 may transmit a path switching request message tothe MME/S-GW 5 c-04 to switch the bearer established towards the sourceeNB 5 c-02 to a bearer established towards the target eNB 5 c-03 at step5 c-60 and receive a path switching request ACK from the MME/S-GW 5 c-04at step 5 c-65. Upon receipt of the path switching request ACK, thetarget eNB 5 c-03 transmits a UE context release message to the sourceeNB 5 c-02 at step 5 c-70. The UE attempts receiving data from thetarget eNB 5 c-03 at the time point of the RAR window and startstransmission to the target eNB 5 c-03 after transmitting theRRCConnectionReconfigurationComplete message since the receipt of theRAR.

In the LTE handover procedure of FIG. 5C, the UE cannot transmit/receivedata during the period between the time point when the HO commandmessage (RRCConnectionReconfiguration) is received and the time pointwhen the UE transmits the HO complete message(RRCConnectionReconfigurationComplete), i.e., the handover to the targeteNB has been completed. Such data transmission suspension causes datatransmission/reception delay. The present disclosure proposes a methodfor minimizing the data transmission suspension time and elaborateoperation to achieve the desired result.

The data transmission suspension time minimization method of the presentdisclosure is called RACH-less handover. The RACH-less handover methodis characterized in that the handover of a UE from a source eNB to atarget eNB is performed without the legacy random access procedure byallowing the UE to transmit the RRCConnectionReconfigurationCompletemessage immediately on the uplink resources pre-allocated by the targeteNB. For this reason, the RACH-less handover method of the presentdisclosure may also be called random access-free handover. There can bevarious embodiments of the RACH-less handover method. The RACH-lesshandover may be implemented with any of various embodiments of thepresent disclosure. The embodiments of the present disclosure aredescribed hereinafter.

FIG. 5D illustrates a RACH-less handover method proposed in the presentdisclosure.

In FIG. 5D, the source eNB 5 d-02 may transmit a UECapabilityEnquirymessage to the UE 5 d-01 to request for UE capability information atstep 5 d-05.

The UE 5 d-01 may transmit a UECapabilityInformation message to thesource eNB 5 d-02 to report per-band or per-bandcombination RACH-lesshandover capability at step 5 d-10. If the source eNB 5 d-02 supportsthe per-band or per-bandcombination RACH-less handover, the RACH-lesshandover can be performed.

The UE 5 d-01 in the connected mode transmits cell measurementinformation (Measurement Report) to the source eNB 5 d-02 at step 5d-15, the measurement information being transmitted periodically or whena predetermined event occurs. The source eNB 5 d-02 makes a handoverdecision based on the measurement information. If the handover decisionis made, the source eNB 5 d-02 transmits a handover request message tothe target eNB 5 d-03 at step 5 d-20.

The source eNB 5 d-02 may further determine whether to perform theRACH-less handover for the UE 5 d-01. In this case, the source eNB 5d-02 requests to the target eNB 5 d-03 for the RACH-less handover atstep 5 d-20. In order to request for the RACH-less handover, the sourceeNB 5 d-02 may include a RACH-less handover indicator (Indication 1) inthe handover request message.

If the target eNB 5 d-03 accepts the handover request, it transmits anHO request Ack message to the source eNB 5 d-02 at step 5 d-25. The HOrequest Ack message include target eNB configuration information for usein the handover procedure. If the target eNB 5 d-03 supports theRACH-less handover, the configuration information may include at leastone of an indicator indicating supportability of RACH-less handover(Indication 2) and information on the uplink resources for use intransmitting an RRC message (RRCConnectionReconfigurationComplete) fromthe UE 5 d-01 to the target eNB 5 d-03. Here, the indicator (Indication2) indicating that the target eNB 5 d-03 supports the RACH-less handovermay be referred to as RACH-less handover indicator or RACH-less handoveractivation information.

The configuration information may also include timing advance or timingadjustment information and, if the timing advance or timing adjustmentinformation is not included, the UE 5 d-01 may apply the same timingadvance or timing advancement information as the source eNB 5 d-02.Meanwhile, the HO request Ack message being transmitted from the targeteNB 5 d-03 to the source eNB 5 d-02 may not include the information onthe uplink transmission resources. That is, the HO request Ack messagemay include the information on the uplink transmission resourceoptionally.

If the HO request Ack message includes uplink transmission resourceinformation, this may mean that the UE 5 d-01 has already acquired theuplink transmission resource through an RRC message.

If the HO request Ack message includes no uplink transmission resourceinformation (if the UE 5 d-01 receives no uplink transmission resourceinformation, the UE 5 d-01 may monitor PDCCH of the target eNB 5 d-03for the control information including the uplink resource information.The detailed description thereof is made later.

The source eNB 5 d-02 transmits the RRCConnectionReconfiguration messageincluding an HO command to the UE 5 d-01 at step 5 d-30. TheRRCConnectionReconfiguration message may include the RACH-less handoverindicator (Indication 2) and information on the uplink transmissionresources for use in transmitting an RRC message(RRCConnectionReconfigurationComplete) from the UE 5 d-01 to the targeteNB 5 d-03. If the handover command is received, the UE 5 d-01 stopsdata communication with the source eNB 5 d-02 and starts a T304 timer atstep 5 d-35. The T304 timer value may be included in theRRCConnectionReconfiguration message transmitted by the source eNB 5d-02. The T304 timer may be a timer for use in determining whether thehandover fails.

If the handover to the target eNB 5 d-03 is not completed before theT304 timer expires, the UE 5 d-01 restores the previous settings andtransitions to the RRC idle state.

As to be described later, the target eNB 5 d-03 may include a separatetimer value (second timer) in the HO request Ack message in addition tothe T304 timer value (first timer) for use in determination whether thehandover is successful. The second timer may be used for the UE toreceive the uplink resource information through PDCCH when the HOrequest Ack message transmitted by the target eNB includes no uplinkresource information.

The source eNB 5 d-02 may include the second timer value in the HOcommand message in order for the UE 5 d-01 to start the second timerand, if no control information is received through PDCCH until thesecond timer expires, perform a random-access procedure. The detaileddescription thereof is made later.

The source eNB 5 d-02 transmits Sequence Number (SN) status informationof uplink/downlink data to the target eNB 5 d-03 at step 5 d-40 and, ifthere is downlink data to transmit, forwards the downlink data to thetarget eNB 5 d-03 at step 5 d-45.

If the RACH-less handover indicator is received at step 5 d-30, the UE 5d-01 performs the RACH-less handover operation. That is, the UE 5 d-01transmits the RRCConnectionReconfigurationComplete message to the targeteNB 5 d-03 at step 5 d-50 using the uplink resource indicated in theRRCConnectionReconfiguration message received at step 5 d-30 instead ofperforming the random access procedure, i.e., steps 5 c-40 and 5 c-45 ofFIG. 5C. If the RRCConnectionReconfiguration message received at step 5d-30 includes no RACH-less handover indicator, the UE 5 d-01 performsthe handover operations as described with reference to FIG. 5C.

If the handover is completed successfully, the UE 5 d-01 stops the T304timer at step 5 d-55. The target eNB 5 d-03 transmits a path switchingrequest to the MME/S-GW at step 5 d-60, receives a path switchingrequest Ack from the MME/S-GW at step 5 d-65, and transmits a UE contextrelease message to the source eNB at step 5 d-70.

FIG. 5E illustrates another RACH-less handover method proposed in thepresent disclosure.

In FIG. 5E, the source eNB 5 e-02 may transmit a UECapabilityEnquirymessage to the UE 5 e-01 to request for UE capability information atstep 5 e-05.

The UE 5 e-01 may transmit a UECapabilityInformation message to thesource eNB 5 e-02 to report per-band or per-bandcombination RACH-lesshandover capability at step 5 d-10. If the source eNB 5 e-02 supportsthe per-band or per-bandcombination RACH-less handover, the RACH-lesshandover can be performed.

The UE 5 e-01 in the connected mode transmits cell measurementinformation (Measurement Report) to the source eNB 5 e-02 at step 5e-15, the measurement information being transmitted periodically or whena predetermined event occurs. The source eNB 5 e-02 makes a handoverdecision based on the measurement information. If the handover decisionis made, the source eNB 5 e-02 transmits a handover request message tothe target eNB 5 e-03 at step 5 e-20.

The source eNB 5 e-02 may further determine whether to perform theRACH-less handover for the UE 5 e-01. In this case, the source eNB 5e-02 requests to the target eNB 5 e-03 for the RACH-less handover atstep 5 e-20. In order to request for the RACH-less handover, the sourceeNB 5 e-02 may include a RACH-less handover indicator (Indication 1) inthe handover request message.

If the target eNB 5 e-03 accepts the handover request, it transmits anHO request Ack message to the source eNB 5 e-02 at step 5 e-25. The HOrequest Ack message include target eNB configuration information for usein the handover procedure. If the target eNB 5 e-03 supports theRACH-less handover, the configuration information may a RACH-lesshandover (Indication 2). Here, the indicator (Indication 2) indicatingthat the target eNB 5 d-03 supports the RACH-less handover may bereferred to as RACH-less handover indicator.

As described above, the HO request Ack message may not include anyuplink resource information.

The source eNB 5 e-02 transmits the RRCConnectionReconfiguration messageincluding an HO command to the UE 5 e-01 at step 5 e-30. TheRRCConnectionReconfiguration message may include the RACH-less handoverindicator (Indication 2). If the RRCConnectionReconfiguration message isreceived, the UE 5 e-01 stops data communication with the source eNB 5e-02 and starts a T304 timer at step 5 e-35. The T304 timer value may beincluded in the RRCConnectionReconfiguration message transmitted by thesource eNB 5 e-02.

The T304 timer is used for the UE 5 e-01 to recover the previoussettings and transition to the RRC idle state when the handover is notcompleted until the T304 timer expires.

The source eNB 5 e-02 transmits Sequence Number (SN) status informationof uplink/downlink data to the target eNB 5 e-03 at step 5 e-40 and, ifthere is downlink data to transmit, forwards the downlink data to thetarget eNB 5 e-03 at step 5 e-45.

If the RACH-less handover indicator is received at step 5 e-30, the UE 5e-01 performs the RACH-less handover operation. That is, the UE 5 e-01may perform a synchronization process with the target eNB 5 e-03 insteadof the random access procedure, i.e., steps 5 c-40 and 5 c-45 and thenmonitors PDCCH for uplink resource allocation information at step 5e-55.

Here, the UE 5 e-01 has already received the handover command from thesource eNB 5 e-02, it camps on the target cell 5 e-03 to achievesynchronization and monitors PDCCH of the target eNB 5 e-03.

The target eNB 5 e-03 allocates uplink resources to the UE through PDCCHin order for the UE 5 e-1 to complete the handover procedure at step 5e-55. If the UE 5 e-01 is allocated the uplink resources, it transmitsthe RRCConnectionReconfigurationComplete message using the allocatedresources at step 5 e-60.

As described above, the target eNB 5 e-03 may include the second timervalue in the handover request Ack message in addition to the first timervalue (T304) for use in determining whether the handover is completedsuccessfully. If the control information is not received through PDCCHuntil the second timer expires, the UE 5 e-01 may trigger the randomaccess procedure. The detailed description thereof is made layer.

If the RRCConnectionReconfiguration message received at step 5 e-30includes no RACH-less handover indicator, the UE 5 e-01 performs thehandover operation as described with reference to FIG. 5C. If thehandover procedure is completed successfully, the UE 5 e-01 stops theT304 timer at step 5 e-65. The target eNB may transmit a path switchingrequest message to the MME/S-GW 5 e-04 to switch the bearer establishedtowards the source eNB 5 e-02 to a bearer established towards the targeteNB 5 e-03 at step 5 e-70, receive a path switching request ACK from theMME/S-GW 5 e-04 at step 5 e-75, and transmit a UE context releasemessage to the source eNB 5 e-02 at step 5 e-80.

Meanwhile, if the UE 5 e-01 cannot be not allocated uplink resourcestowards the target eNB 5 e-03 for any reason in the RACH-less handoverprocedure, it has to wait until the T304 timer expires. The T304 timermay run for a long time because its smallest value is 100 ms and thusthe elongated transmission suspension time may cause data transmissioninterruption phenomenon. The present disclosure proposes a method forconfiguring a UE-initiated timer (timer 1) or a network-initiated timer(timer 2) in order to reduce the data transmission suspension time. Asdescribed above, the T304 timer may be called first timer, and theUE-initiated or network-initiated timer (timer 2) for use in reducingdata transmission suspension time may be called second timer.

FIG. 5F illustrates a RACH-less handover procedure for reducing datatransmission suspension time by configuring a UE-initiated timer (Timer1) especially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason.

The handover procedure of FIG. 5F is similar to that of FIG. 5E. Steps 5f-05 to 5 f-45 of FIG. 5F are identical with steps 5 e-05 to 5 e-45 ofFIG. 5E and thus detailed descriptions thereof are omitted herein.

If an RRCConnectionReconfiguration message including the RACH-lesshandover indicator (Indication 2) is received at step 5 f-30, the UE 5f-01 may achieve synchronization with the target eNB 5 f-03 at step 5f-50.

If the synchronization has been achieved, the UE 5 f-01 starts Timer 1at step 5 f-55. Timer 1 is running on the UE 5 f-01 and may be set to avalue less than the T304.

As to be described later, the UE 5 f-01 may receive a second timer valueless than the timer T304 from the target eNB 5 f-03 and start a timerset to the second timer value. For example, the target eNB 5 f-03 maytransmit the timer value using the handover request Ack message.

Accordingly, the UE 5 f-01 may receive the second timer value (e.g., 50ms) from the target eNB 5 f-03 in addition to the legacy T304 timervalue and starts the second timer. The UE 5 f-01 may use this timervalue for its own timer or use the T304 timer.

Also, the T304 timer value may be included in the MobilityControlInfo ofthe RRCConnectionReconfiguration message, i.e., the handover commandmessage, transmitted from the source eNB 5 f-02 to the UE 5 f-01. Forexample, the T304 timer may be set to 100 ms for normal handover or 50ms for RACH-less handover.

If it fails to receive uplink resource allocation information from thetarget eNB 5 f-03 for any reason before the timer 1 expires at step 5f-60, the UE 5 f-01 triggers the random access procedure (fallback tothe random access procedure) by transmitting a random access preamble atstep 5 f-65. If a random access response is received in response to therandom access preamble at step 5 f-70, the UE 5 f-01 stops the T304timer at step 5 f-75. Then the UE 5 f-01 performs an RRC connectionreestablishment procedure with the target eNB 5 f-03 at steps 5 f-80, 5f-85, and 5 f-90.

FIG. 5G illustrates another RACH-less handover procedure for reducingdata transmission suspension time by configuring a UE-initiated timerespecially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason.

The handover procedure of FIG. 5G is similar to that of FIG. 5E. Steps 5f-05 to 5 f-45 of FIG. 5G are identical with steps 5 e-05 to 5 e-45 ofFIG. 5E and thus detailed descriptions thereof are omitted herein.

If an RRCConnectionReconfiguration message including the RACH-lesshandover indicator (Indication 2) is received at step 5 g-30, the UE 5g-01 may achieve synchronization with the target eNB 5 g-03 at step 5g-50.

If the synchronization has been achieved, the UE 5 g-01 starts Timer 1at step 5 g-55. Timer 1 is running on the UE 5 g-01 and may be set to avalue less than the T304.

As described above, the UE 5 g-01 may receive a second timer value fromthe target eNB 5 f-03 and start a timer set to the second timer value.The detailed description thereof has been made above and thus is omittedherein.

If it fails to receive uplink resource allocation information from thetarget eNB 5 g-03 for any reason before timer 1 expires at step 5 g-60,the UE 5 g-01 triggers the random access procedure (fallback to therandom access procedure). If no uplink resource is allocated by thetarget eNB 5 g-03, the target eNB 5 g-03 may not be the best eNB.

Accordingly, the UE 5 g-01 performs a cell reselection procedure tosearch for the best eNB at step 5 g-65. Then the UE 5 g-01 performs therandom access procedure with the newly found eNB 5 g-04 at step 5 g-70and 5 g-75.

If the random access response is successfully received from the newtarget eNB 5 g-04, the UE 5 g-01 stops the T304 timer at step 5 g-80. Ifthe random access procedure has been successfully completed, the UE 5g-01 performs the RRC connection reestablishment procedure with the newtarget eNB 5 g-04. That is, if a random access response is successfullyreceived at step 5 g-75, the UE 5 g-01 transmits aRRCConnectionReestablishmentRequest message to the new target eNB 5 g-04at step 5 g-85.

If the RCCConnectionReestablishmentRequest message is received, the newtarget eNB 5 g-04 transmits a Radio Link Failure (RLF) indicator to thesource eNB 5 g-02 at step 5 g-90, and the source eNB 5 g-02 transmits ahandover cancel message to the old target eNB 5 g-03 at step 5 g-95.

Then, the source eNB 5 g-02 transmits a handover request message to thenew target eNB 5 g-04 at step 5 g-100, and the new target eNB 5 g-04transmits a handover request Ack message to the source eNB 5 g-02 atstep 5 g-105.

Afterward, the source eNB 5 g-02 transmits Sequence Number (SN) statusinformation to the new target eNB 5 g-04 at step 5 g-110 and, if thereis downlink data to transmit, forwards the data to the new target eNB 5g-04 at step 5 g-15. If the SN status information and data are receivedat steps 5 g-110 and 5 g-115, the new target eNB 5 g-04 transmits anRCCConnectionReestablishment message to the UE 5 g-01 at step 5 g-120,and the UE 5 g-01 transmits an RRCConnectionReestablishmentCompletemessage at step 5 g-125, thereby completing RRC connectionreestablishment.

The procedures of FIGS. 5F and 5G are directed to the use ofUE-initiated timer (Timer 1) to reduce data transmission suspensiontime. However, by taking notice that the uplink resource allocation forthe UE to be handed over is made by the target eNB, it may be possiblefor the target eNB to determine more suitable timer value. Accordingly,the present disclosure proposes a network-initiated timer (Timer 2)configuration method in which the target eNB determines the timer value.

FIG. 5H illustrates a RACH-less handover procedure for reducing datatransmission suspension time by configuring a network-initiated timer(Timer 2) especially when a UE cannot be allocated uplink resources fortransmission to a target eNB for any reason.

The handover procedure of FIG. 5H is similar to that of FIG. 5E.

In this handover procedure, the target eNB 5 h-03 may transmit to thesource eNB 5 h 02 an HO request Ack message including the second timervalue (Timer 2) at step 5 h-25. Here, the second timer value may be lessthan the timer value of T304, i.e., 100 ms, because the smallest valueof T304 is 100 ms.

The UE 5 h-01 may acquire the RACH-less handover indicator (Indication2) and Timer 2 from the RRCConnectionReconfiguration message transmittedby the source eNB 5 h-02 at step 5 h-30. Afterward, the UE 5 h-01 mayachieve synchronization with the target eNB 5 h-03 at step 5 h-50. Thehandover-related steps of FIG. 5H are identical with those of FIG. 5E.That is, steps 5 h-05 to 5 h-45 of FIG. 5H are identical with steps 5e-05 to 5 e-45 of FIG. 5E.

If the synchronization has been achieved, the UE 5 h-01 starts Timer 2at step 5 h-55. Timer 2 is set to the value recommended by the targeteNB 5 h-03, and the Timer 2 value may be less than the T304 timer value.

If it fails to receive uplink resource allocation information from thetarget eNB 5 h-03 for any reason before Timer 2 expires at step 5 h-60,the UE triggers a random access procedure by transmitting a randomaccess preamble at step 5 h-65 (fallback to random access procedure). Ifa random access response is successfully received from the target eNB 5h-03 in response to the random access preamble, the UE 5 h-01 stops theT304 timer at step 5 h-75. Then, the UE 5 h-01 performs an RRCconnection reestablishment procedure with the target eNB 5 h-03 at steps5 h-80, 5 h-85, and 5 h-90.

In this procedure, the source eNB 5 h-02 may reuse the T304 timer ratherthan Timer 2. That is, the source eNB 5 h-02 may set the T304 timer tothe Timer 2 value received from the target eNB 5 h-03 at step 5 h-25.

FIG. 5I illustrates another RACH-less handover procedure for reducingdata transmission suspension time by configuring a network-initiatedtimer (Timer 2) especially when a UE cannot be allocated uplinkresources for transmission to a target eNB for any reason.

The handover procedure of FIG. 5I is similar to that of FIG. 5E.

In this handover procedure, the target eNB 5 i-03 may transmit to thesource eNB 5 h-02 an HO request Ack message including the second timervalue (Timer 2) at step 5 h-25. Here, the second timer value may be lessthan the T304 timer value, i.e., 100 ms, because the smallest value ofT304 is 100 ms.

The UE 5 i-01 may acquire the RACH-less handover indicator (Indication2) and Timer 2 from the RRCConnectionReconfiguration message transmittedby the source eNB 5 i-02 at step 5 i-30. Afterward, the UE 5 i-01 mayachieve synchronization with the target eNB 5 i-03 at step 5 i-50. Thehandover-related steps of FIG. 5I are identical with those of FIG. 5E.That is, steps 5 i-05 to 5 i-45 of FIG. 5 i are identical with steps 5e-05 to 5 e-45 of FIG. 5E.

If the synchronization has been achieved, the UE 5 i-01 starts Timer 2at step 5 i-55. Timer 2 is set to the value recommended by the targeteNB 5 h-03, and the Timer 2 value may be less than the T304 timer value.

If it fails to receive uplink resource allocation information from thetarget eNB 5 i-03 for any reason before Timer 2 expires at step 5 i-60,the UE 5 i-01 triggers the random access procedure (fallback to therandom access procedure). If no uplink resource is allocated by thetarget eNB 5 i-03, the target eNB 5 i-03 may not be the best eNB.

Accordingly, the UE 5 i-01 performs a cell reselection procedure tosearch for the best eNB at step 5 i-65. Then the UE 5 i-01 performs therandom access procedure with the newly found eNB 5 i-04 at step 5 i-70and 5 i-75. If the random access response is successfully received fromthe new target eNB 5 i-04, the UE 5 i-01 stops the T304 timer at step 5i-80. If the random access procedure has been successfully completed,the UE 5 i-01 performs the RRC connection reestablishment procedure withthe new target eNB 5 i-04. That is, if a random access response issuccessfully received at step 5 i-75, the UE 4 i-01 transmits aRRCConnectionReestablishmentRequest message to the new target eNB 5 i-04at step 5 i-85.

If the RCCConnectionReestablishmentRequest message is received, the newtarget eNB 5 i-04 transmits a Radio Link Failure (RLF) indicator to thesource eNB 5 i-02 at step 5 i-90, and the source eNB 5 i-02 transmits ahandover cancel message to the old target eNB 5 i-03 at step 5 i-95.

Then, the source eNB 5 i-02 transmits a handover request message to thenew target eNB 5 i-04 at step 5 i-100, and the new target eNB 5 i-04transmits a handover request Ack message to the source eNB 5 i-02 atstep 5 i-105.

Afterward, the source eNB 5 i-02 transmits Sequence Number (SN) statusinformation to the new target eNB 5 i-04 at step 5 i-110 and, if thereis downlink data to transmit, forwards the data to the new target eNB 5i-04 at step 5 i-115. If the SN status information and data are receivedat steps 5 i-110 and 5 i-115, the new target eNB 5 i-04 transmits anRCCConnectionReestablishment message to the UE 5 i-01 at step 5 i-120,and the UE 5 i-01 transmits an RRCConnectionReestablishmentCompletemessage at step 5 i-125, thereby completing RRC connectionreestablishment.

In this procedure, the source eNB 5 i-02 may reuse the T304 timer ratherthan Timer 2. That is, the source eNB 5 i-02 may set the T304 timer tothe Timer 2 value received from the target eNB 5 i-03 at step 5 i-25. Inthe proposed RACH-less handover procedure of the present disclosure,when it fails to receive uplink resource allocation information from thetarget eNB, the UE may store and report the failure information to thenetwork for use later. Even when the UE fails to receive uplink resourceallocation information from the target eNB and then attempts a randomaccess procedure to connect a new target eNB, it may store and reportthe related information to the network for use later.

FIG. 5J illustrates a UE operation according to the present disclosure.

In FIG. 5J, the UE may receive a UECapabilityEnquiry message from thesource eNB. In response to the UECapabilityEnquiry message, the UE maytransmit UE capability information (UECapability) to the source eNB atstep 5 j-01.

The UE capability information may include per-band orper-bandcombination RACH-less handover capability.

The UE may transmit cell measurement information to the source eNBperiodically or when a predetermined event occurs, and the source eNBmay make a handover decision based on the measurement information.

If the handover decision has been made positively, the UE may receive ahandover command message (RRCConnectionReconfiguration) from the sourceeNB at step 5 j-02. Upon receipt of the handover command message at step5 j-02, the UE may start a T304 timer.

The UE determines at step 5 j-10 whether the handover command messageincludes a RACH-less handover indicator. If it is determined that theRACH-less handover indicator is not included in the handover commandmessage, the UE performs the legacy LTE handover procedure at step 5j-15. That is, the UE triggers a random access procedure to the targeteNB. If a Random Access Response (RAR) is successfully received from thetarget eNB, the UE stops the T304 timer at step 5 j-20.

If it is determined that the RACH-less handover indicator is included inthe handover command message, the UE establishes a connection to thetarget eNB by transmitting a handover complete message(RRCConnectionReconfigurationComplete) using the uplink resourcesindicated in the message at step 5 j-25. If the connection to the targeteNB is successfully configured, the UE stops the T304 timer at step 5j-30.

Here, the uplink resource allocation information may be included in thehandover command message. Accordingly, the UE may transmit the handovercomplete message to the target eNB using the resources indicated by theuplink resource allocation information in the handover command message.

If the handover command message includes no uplink resource allocationinformation, the UE may monitor PDCCH of the target eNB for controlinformation to acquire the uplink transmission resource information. TheUE may transmit the handover complete message to the target eNB based onthe uplink transmission resource information.

The handover command message may include the second timer value but notthe uplink transmission resource information and, in this case, the UEmay start a timer set to the second timer value to perform the randomaccess procedure upon expiry of the timer.

FIG. 5K illustrates another UE operation according to the presentdisclosure.

In FIG. 5K, the UE may receive a UECapabilityEnquiry message from thesource eNB. In response to the UECapabilityEnquiry message, the UE maytransmit UE capability information (UECapability) to the source eNB atstep 5 k-01.

The UE capability information may include per-band orper-bandcombination RACH-less handover capability.

The UE may transmit cell measurement information to the source eNBperiodically or when a predetermined event occurs, and the source eNBmay make a handover decision based on the measurement information.

If the handover decision has been made positively, the UE may receive ahandover command message (RRCConnectionReconfiguration) from the sourceeNB at step 5 k-02. Upon receipt of the handover command message at step5 k-02, the UE may start a T304 timer. The T304 timer value may bereferred to as first timer value.

The UE determines at step 5 k-10 whether the handover command messageincludes a RACH-less handover indicator. If it is determined that theRACH-less handover indicator is not included in the handover commandmessage, the UE performs the legacy LTE handover procedure as describedwith reference to FIG. 5C at step 5 k-15.

Otherwise, if it is determined that the RACH-less handover indicator isincluded in the handover command message, the UE may achievesynchronization with the target eNB and monitors physical downlinkcontrol channel (PDCCH) of the target eNB at step 5 k-20. In this case,the UE starts Timer X set to the second timer value.

The second timer value may be configured by the UE as described withreference to FIG. 5F or by the target eNB as described with reference toFIG. 5H. If the second timer value is configured by the target eNB, itmay be transmitted to the UE through the handover command message.

The UE may determine at step 5 k-25 whether the Timer X has expired. Ifit is determined that the timer X has expired, the UE performs thelegacy LTE handover procedure as described with reference to FIG. 5C atstep 5 k-30. That is, the UE triggers the random access procedure to thetarget eNB. If a RAR is successfully received from the target eNB, theUE stops the T304 timer at step 5 k-35.

If it is determined at step 5 k-25 that the timer X has not expired, theUE determines at step 5 k-40 whether an uplink grant is received fromthe target eNB. If it is determined at step 5 k-40 that the uplink grantis received, the UE stops the timer X and T304 timer at step 5 k-45.

Then, the UE transmits an RRCConnectionReconfigurationComplete messageto the target eNB using the uplink transmission resources indicated bythe uplink grant to establishes a connection at step 5 k-50. The T304timer may expire after RRCConnectionReconfigurationComplete message hasbeen transmitted.

FIG. 5L illustrates another UE operation according to the presentdisclosure.

In FIG. 5L, the UE may receive a UECapabilityEnquiry message from thesource eNB. In response to the UECapabilityEnquiry message, the UE maytransmit UE capability information (UECapability) to the source eNB atstep 5 l-01.

The UE capability information may include per-band orper-bandcombination RACH-less handover capability.

The UE may transmit cell measurement information to the source eNBperiodically or when a predetermined event occurs, and the source eNBmay make a handover decision based on the measurement information.

If the handover decision has been made positively, the UE may receive ahandover command message (RRCConnectionReconfiguration) from the sourceeNB at step 5 l-02. Upon receipt of the handover command message at step5 l-02, the UE may start a T304 timer. The T304 timer value may bereferred to as first timer value.

The UE determines at step 5 l-10 whether the handover command messageincludes a RACH-less handover indicator. If it is determined that theRACH-less handover indicator is not included in the handover commandmessage, the UE performs the legacy LTE handover procedure as describedwith reference to FIG. 5C at step 5 l-15.

Otherwise, if it is determined that the RACH-less handover indicator isincluded in the handover command message, the UE may achievesynchronization with the target eNB and monitors PDCCH of the target eNBat step 5 l-20. In this case, the UE starts Timer X set to the secondtimer value.

The second timer value may be configured by the UE as described withreference to FIG. 5F or by the target eNB as described with reference toFIG. 5H. If the second timer value is configured by the target eNB, itmay be transmitted to the UE through the handover command message.

The UE may determine at step 5 l-25 whether the Timer X has expired. Ifit is determined that the timer X has expired, the UE performs a cellreselection procedure at step 5 l-30. At step 5 l-35, the UE performsthe random access procedure to the eNB with the best signal strengthwhich has been selected through the cell reselection procedure. If arandom access response (RAR) is successfully received from the targeteNB, the UE stops the T304 timer at step 5 l-40.

If it is determined at step 5 l-25 that the timer X has not expired, theUE determines at step 5 l-45 whether an uplink grant is received fromthe target eNB. If it is determined at step 5 l-45 that the uplink grantis received, the UE stops the timer X and T304 timer at step 5 l-50.

Then, the UE transmits an RRCConnectionReconfigurationComplete messageto the target eNB using the uplink transmission resources indicated bythe uplink grant to establishes a connection at step 5 l-55. The T304timer may expire after RRCConnectionReconfigurationComplete message hasbeen transmitted.

FIG. 5M illustrates a configuration of a UE according to an embodimentof the present disclosure.

In reference to FIG. 5M, the UE includes transceiver 5 m-05, acontroller 5 m-10, a multiplexer/demultiplexer 5 m-15, a control messageprocessor 5 m-30, higher layer processors 5 m-20 and 5 m-25, an EPSbearer manager 5 m-35, and a NAS layer entity 5 m-40. In the presentdisclosure, the controller 5 m-10 may be interchangeably referred to asa circuit, an application-specific integrated circuit, and at least oneprocessor and the controller may be coupled with the transceiver.

The transceiver 5 m-05 receives data and predetermined control signalsthrough downlink channels of a serving cell and transmits data andpredetermined control signals through uplink channels. In the case thatmultiple serving cells are configured, the transceiver 5 m-05 maytransmit and receive the data and control signals through the multipleserving cells.

The multiplexer/demultiplexer 5 m-15 may multiplex the data generated bythe higher layer processors 5 m-20 and 5 m-25 and the control messageprocessor 5 m-30 or demultiplex the data received by the transceiver 5m-05 and deliver the demultiplexed data to the corresponding higherlayer processors 5 m-20 and 5 m-25 or the control message processor 5m-30.

The control message processor 5 m-30 is an RRC layer entity forprocessing the control messages received from an eNB and take anoperation according to the processing result. For example, if an RRCCONNECTION SETUP message is received, the control message processor 5m-3—configures a Signaling Radio Bearer (SRB) and a temporary DedicatedRadio Bearer (DRB).

The higher layer processor is a DRB entity which is established perservice. The higher layer processors 5 m-20 and 5 m-25 process the userservice data such as File Transfer Protocol (FTP) and Voice overInternet Protocol (VoIP) data and send the processing output to themultiplexer/demultiplexer 5 m-15 or process the data from themultiplexer/demultiplexer 5 m-15 and deliver the processing output tohigher layer service applications. A service may be mapped to an EPSbearer and a higher layer entity one by one.

The controller 5 m-10 checks for the scheduling command, e.g., uplinkgrants, received by the transceiver 5 m-05 and controls the transceiver5 m-05 and the multiplexer/demultiplexer 5 m-15 to perform uplinktransmission with appropriate transmission resources at an appropriatetiming.

In detail, the controller 5 m-10 may control the signaling among thefunction blocks to accomplish the operations according to the proceduresdescribed with reference to the above flowcharts. In more detail, thecontroller 5 m-10 may control the transceiver 5 m-05 to receive a UEcapability enquiry (UECapabilityEnquiry) message from the source eNB andtransmit UE capability (UECapability) information to the source eNB.

The UE capability information may include a band-specific or abandcombination-specific RACH-less handover indicator.

The controller 5 m-10 may control the transceiver 5 m-05 to receive ahandover command message (RRCConnectionReconfiguration) from the sourceeNB. If the handover command message is received, the controller 5 m-10starts the T304 timer.

The controller 5 m-10 also determines whether the handover commandmessage includes a RACH-less handover indicator.

If the RACH-less handover indicator is included in the handover commandmessage, the controller 5 m-10 controls the transceiver 5 m-05 totransmit a handover complete message(RRCConnectionReconfigurationComplete) using the uplink resourcesindicated in the handover command message. If the connection to thetarget eNB is successfully configured, the controller 5 m-10 stops theT304 timer

Here, the uplink resource allocation information may be included in thehandover command message. Accordingly, the controller 5 m-05 may controlthe transceiver 5 m-05 to transmit the handover complete message to thetarget eNB using the resources indicated by the uplink resourceallocation information in the handover command message.

If the handover command message includes no uplink resource allocationinformation, the controller 5 m-10 may control the UE to monitor PDCCHof the target eNB for control information to acquire the uplinktransmission resource information. The controller 5 m-10 may control thetransceiver 5 m-05 to transmit the handover complete message to thetarget eNB based on the uplink transmission resource information.

The handover command message may include the second timer value but notthe uplink transmission resource information and, in this case, thecontroller 5 m-10 may start a timer set to the second timer value toperform the random access procedure upon expiry of the timer.

The controller 5 m-10 may also control other operations of the UE asproposed in the present disclosure.

FIG. 5N illustrates a configuration of an eNB including an MME part anda S-GW part according to an embodiment of the present disclosure, andthe eNB includes transceiver 5 n-05, a controller 5 n-10 amultiplexer/demultiplexer 5 n-20, a control message processor 5 n-35,higher layer processors 5 n-25 and 5 n-30, a scheduler 5 n-15, EPSbearer entities 5 n-40 and 5 n-45, and a NAS entity 5 n-50.

The transceiver 5 n-05 transmits data and predetermined control signalsthrough downlink channels of a serving cell and receives data andpredetermined control signals through uplink channels. In the case thatmultiple serving cells are configured, the transceiver 5 n-05 maytransmit and receive the data and control signals through the multipleserving cells.

The multiplexer/demultiplexer 5 n-20 may multiplex the data generated bythe higher layer processors 5 n-25 and 5 m-30 and the control messageprocessor 5 n-35 or demultiplex the data received by the transceiver 5n-05 and deliver the demultiplexed data to the corresponding higherlayer processors 5 n-2 n and 5 n-30 or the control message processor 5n-35. The control message processor 5 n-35 processes the controlmessages received from a UE to take an operation according to theprocessing result and generates a control message to be transmitted tothe UE to the lower layers.

The higher layer processor may be established per EPS bearer; the higherlayer processors 5 n-25 and 5 n-30 process the data from thecorresponding EBS bearer entities 5 n-40 and 5 n-45 to generate RLC PDUsto the multiplexer/demultiplexer 5 n-20 or processes the RLC PDUs fromthe multiplexer/demultiplexer 5 n-20 into PDCP SDUs to the correspondingEPS bearer entities 5 n-40 and 5 n-45.

The scheduler allocates transmission resources to the UE for uplinktransmission at appropriate timing based on UE's buffer status andchannel condition and assists the transceiver 5 n-05 to process thesignals received from the UE and to be transmitted to the UE.

The EPS bearer entity is established per EPS bearer; the EPS bearerentities 5 n-40 and 5 n-45 process the data delivered by thecorresponding higher layer processors 5 n-25 and 5 n-30 into a format tobe transmitted to the next network node.

The higher layer processors 5 n-25 and 5 n-30 and the EPS bearerentities 5 n-40 and 5 n-45 are mutually connected through S1-UE bearers.A higher layer processor corresponding to a common DRB is connected toan EPS bearer entity established the common DRB through a common S1-Ubearer.

The NAS layer entity 5 n-50 processes IP packets contained in a NASmessage and transfers the processing output to an S-GW.

The controller 5 n-10 may controls signaling among the function blocksto accomplish the operations in the procedures described with above. Indetail, as a controller of a first eNB (source eNB), the controller 5n-10 may control the transceiver 5 n-05 to transmit a UE capabilityenquiry (UECapabilityEnquiry) message to a UE and receive UE capabilityinformation (UECapability) from the UE.

The UE capability information may include a band-specific or abandcombination-specific RACH-less handover indicator.

The controller 5 n-10 may control the transceiver 5 n-05 to transmit ahandover request message to a target eNB and receive a handover requestAck message from the target eNB. The handover request Ack message mayinclude at least one of RACH-less handover capability indicator (orRACH-less handover configuration indicator or RACH-less handoverindicator), uplink resource allocation information, and a timer value.

The controller 5 n-10 may also control the transceiver 5 n-05 totransmit a handover command message (RRCConnectionReconfiguration) tothe UE. The handover command message may include the informationcontained in the handover request Ack message.

If the handover command message includes the RACH-less handoverindicator, the UE may transmit a handover complete message to the targeteNB using the uplink resource with no random access procedure.

The UE may use the uplink resource information included in the handovercommand message. if the handover command message includes no uplinkresource information, the UE may monitor PDCCH of the target eNB forcontrol information to acquire the uplink transmission resourceinformation. The UE may transmit the handover complete message using theuplink resources indicated by the uplink transmission resourceinformation.

As a controller of the second eNB (target eNB), the controller 5 n-10may control the transceiver 5 n-05 to receive a handover request messagefrom a source eNB and transmit a handover request Ack message to thesource eNB. The handover request Ack message may include at least one ofRACH-less handover capability indicator (or RACH-less handoverconfiguration indicator or RACH-less handover indicator), uplinkresource allocation information, and a timer value.

The controller 5 n-10 may also control the transceiver 5 n-05 to receivea handover complete message based on the uplink resource information.

The controller 5 n-10 may control the transceiver 5 n-05 to receive thehandover complete message based the uplink resource information includedin the handover command message.

If the handover command message includes not uplink resourceinformation. the controller 5 n-10 may control the transceiver 5 n-05 totransmit the control information including uplink resource informationthrough PDCCH.

The control unit 5 n-10 may include the timer value in the handoverrequest Ack message; and, if the UE fails to receive the controlinformation through PDCCH before expiry of the timer set to the timevalue, it triggers the random access procedure. Here, the timer valuemay be less than the timer value (T304) configured for determininghandover failure.

Sixth Embodiment

The present disclosure proposes a method and apparatus for a normalterminal or a terminal operating in an extended coverage mode(hereinafter, interchangeably referred to as NB-IoT UE, Bandwidthreduced Low complexity (BL) UE, UE in Coverage Enhancement (CE), andenhanced Machine Type Communication (eMTC) UE) to transition to a largepaging area preference mode autonomously and update paging area toreduce battery power consumption.

FIG. 6A illustrates architecture of an LTE system.

The detailed description of the LTE system architecture has been madealready with reference to FIG. 1A and thus is omitted herein.

FIG. 6B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system.

The detailed description of the protocol stack has been made alreadywith reference to FIGS. 2B and 3B and thus is omitted herein.

FIG. 6C illustrates the concept of light connection.

The light connection technique is introduced along with definition of anew UE operation mode in addition to the legacy idle and connected modesto reduce signaling overhead caused by legacy handover and pagingoperations. The newly defined mode may be referred to as light connectedmode, inactive mode, or the like (hereinafter, referred to lightconnected mode).

The UE 6 c-03 in the light connected mode is characterized by the S1connections kept between the MME 6 c-01 and the eNBs 6 c-02 and 6 c-04and in that one of the MME 6 c-01 and the eNBs 6 c-02 and 6 c-04 maytrigger paging.

The MME 6 c-01 assumes that the UE in the light connected mode isoperating in the connected mode; thus, if there is any data to transmitto the UE, the MME 6 c-01 transmits the data to the eNB withouttriggering a paging procedure. If the data is received, the eNBtransmits a paging message to all eNBs within the Paging Area (PA) 6c-05 such that the eNBs broadcast the paging message.

The present disclosure proposes UE and network operations capable ofreducing battery consumption and signaling overhead of the UE inconsideration of the above-described characteristics of a lightconnection.

FIGS. 6DA and 6DB illustrate signal flows among a UE, an anchor eNB, anew eNB, and an MME for UE context and S1 bearer reuse in lightconnection procedure according to the present disclosure.

In FIGS. 6DA and 6DB, it is assumed that the UE in the RRC connectedmode has been communicating data with the anchor eNB. If the datacommunication is stopped, the anchor eNB starts a predetermined timerand, if data communication is not resumed before expiry of the timer atstep 6 d-05, determines to release the RRC connection of the UE.

The eNB stores UE context and transmits to the UE a control messageinstructing release of the RRC connection (RRC connection releasemessage) at step 6 d-10.

The control message may include a Resume ID and paging area information.That is, the eNB allocates a Resume ID to the UE and configure a PA inwhich the UE in the light connected mode to report mobility.

The PA may be comprised of one or more cells. The eNB may transmit tothe UE a list of IDs of the cells constituting the PA of the eNB, andthe UE may determine whether the PA is updated by comparing the cell IDbroadcast by the eNB with the cell IDs contained in cell ID list.

It may also be possible for the eNB to transmit a PA identifier toconfigure a PA for the UE. The network or the eNB may configure a PAwith at least one cell and allocates a PA identifier per PA.Accordingly, if a PA identifier is received, the UE may check the PAidentifier for the list of the cells and make a paging area updatedetermination based on the cell ID being received, on the move, from theeNBs and the PA ID. Detailed description thereof is made later.

The cell list or the PA identifier may be transmitted to the UE throughRRC signaling or broadcast in an SIB.

The UE may be aware of the necessity of preserving the UE context basedon the Resume ID allocation. It may also be possible for the eNB totransmit a control message including a context preservation indicator toinstruct the UE to preserve the UE context. This control message mayinclude context preservation period or a cell list for use in an RRCconnection reconfiguration procedure of the UE during a valid period.

Even after releasing the RRC connection for the UE, the anchor eNBmaintains the UE context and S1 bearer at step 6 d-15.

The S1 bearer includes the S1-control plane bearer for use in exchangingcontrols signal between the eNB and the MME and the S1-user plane bearerfor use in exchanging user data between the eNB and the S-GW. Bymaintain the S1 bearer, it may be possible to skip the S1 bearerconfiguration procedure while the UE tries to establish an RRCconnection in the same cell or eNB. If the valid period expires, the eNBmay delete the UE context and release the S1 bearer.

If the RRC connection release message is received, the UE transitions tothe light connected mode at step 6 d-25.

The eNB transmits to the MME a control message requesting for suspendingthe connection temporarily at step 6 d-20. If this temporarilyconnection suspension request message is received, the MME instructs theS-GW to hold transmitting downlink data for the UE and triggers a pagingprocedure, and the S-GW operates based on the instruction at step 6d-35. Or, the S-GW may forward the downlink data to the anchor eNB, andthe anchor eNB may generate and transmit a paging message to theneighboring eNBs. If downlink data is received, the anchor eNB buffersthe data in a buffer and triggers the paging procedure. The anchor eNBis the eNB which maintains the UE context and maintains the S1-U bearer.

If the RRC connection release message including the context preservationindicator and Resume ID is received at step 6 d-10, the UE releases theRRC connection and starts a timer corresponding to the valid period. TheUE writes the valid cell list in the memory and maintain the UE contextin the memory t step 6-25.

The UE context may the RRC connection-related information of the UE suchas Signaling Radio Bearer (SRB) configuration information, Data RadioBearer (DRB) configuration information, and security key information.

Afterward, it becomes necessary to establish an RRC connection for anyreason at step 6 d-30. A UE for which neither a Resume ID is allocatednor a context preservation is not indicated in the previous RRCconnection release procedure may initiate the legacy RRC connectionsetup procedure.

However, a UE for which a Resume ID is allocated in the previous RRCconnection release procedure may attempts an RRC connection resumeprocedure using the maintained UE context.

In detail, the UE may transmit message 1 including a preamble to triggera random access procedure at step 6 d-40.

If it is determined that resource allocation is available based on thepreamble included in message 1, the eNB transmits message 2 to allocateuplink resources to the UE at step 4 c-45. The message 2 may be a RandomAccess Response (RAR) message.

Upon receipt of the RAR message, the UE transmits a Resume requestmessage including a Resume ID selected based on the uplink resourceinformation to a new eNB at step 6 d-50. The Resume request message maybe a modified RRCConnectionRequest message or a newly defined message(e.g., RRCConnectionResumeRequest).

If the UE which has transitioned from the connected mode to the lightconnected mode camps on a cell of a new eNB, the new eNB may receive theResume ID of the UE and identifies the previous serving eNB of the UEbased on the Resume ID.

If the new eNB receives the Resume ID successfully, it performs aprocedure for retrieving the UE context from the source eNB (ContextRetrieve Procedure) at step 6 d-55. The new eNB may retrieve the UEcontext form the source eNB through an S1 or X2 interface. If the neweNB receives the Resume ID successfully but fails to identify the UE, ithas to transmit a RRCConnectionSetup message to the UE to perform thelegacy RRC connection establishment procedure.

The new eNB checks for the MAC-I based on the UE context retrieved fromthe source eNB at step 6 d-60. The MAC-I is a message authenticationcode computed by the UE using the control message by applying thesecurity information (i.e., security key and security counter) of theretrieved UE context.

The eNB checks for the integrity of the message using the MAC-I of themessage and the security key and security counter included in the UEcontext. The new eNB generates RRC configuration information to beapplied to the UE and transmits the RRC connection resume(RRCConnectionResume) message including the configuration information tothe UE at step 6 d-65.

The RRC connection resume message may be a modified RRC connectionrequest message including the information indicating “RRC context reuse”(REUSE INDICATOR). The RRC connection resume message may include the RRCconnection configuration information for the UE like the RRC connectionsetup message.

Unlike the UE which has received a normal RRC connection setup(RRCConnectionSetup) message configures the RRC Connection based on theconfiguration information included in the RRC connection setup message,a UE which has received the RRC connection resume message configures anRRC connection in consideration of both the maintained configurationinformation and the configuration information included in the RRCconnection resume message (delta configuration).

For example, if the RRC connection resume message is received, the UEstores the configuration information contained in the RRC connectionresume message and checks the configuration information for deltainformation to update the configuration information or UE context. Forexample, if the RRC connection resume message includes SRB configurationinformation, the UE configures an SRB based on the SRB configurationinformation; if the RRC connection resume message does not include SRBconfiguration information, the UE configures an SRB based on the SRBconfiguration information included in the UE context.

The UE configures an RRC connection based on the updated UE context andthe configuration information and transmits an RRC connection resumecomplete message to the new eNB at step 6 d-70.

The new eNB transmits to the MME a control message requesting forreleasing the temporary connection suspension and reconfiguring the S1bearer to the new eNB at step 6 d-75. If this control message isreceived, the MME instructs the S-GW to reconfigure the S1 bearer withthe new eNB and handle the data for the UE normally.

If the RRC connection reconfiguration procedure has been completed, theUE resumes data communication through the corresponding cell at step 6d-80. In the above procedure, if the UE in the light connected modemoves but not much and thus camps on the cell of the source eNB again,the source eNB may retrieve the UE context based on the Resume IDincluded in message 3 and configured the connection based on the UEcontext in a procedure like those described above.

If the data communication is stopped, the eNB starts a predeterminedtimer and, if data transmission is not resumed before expiry of thetimer at step 6 d-5, determines to release the RRC connection of the UE.

In this case, the eNB may store UE context and transmit to the UE acontrol message instructing release of the RRC connection (RRCconnection release message) at step 6 d-90. The eNB allocates a ResumeID to the UE and configure a PA in which the UE in the light connectedmode to report mobility. That is, the eNB may include the Resume ID andPA information in the RRC connection release message. The PAconfiguration method is similar to that described above and thusdetailed description thereof is omitted herein. If the RRC connectionrelease message is received, the UE transitions to the light connectedmode at step 6 d-95.

As described above, the UE may transition to the light connected mode(or inactive mode) upon receipt of the RRC connection release messageand, if it moves out of the paging area in the light connected mode,updates the PA.

FIG. 6E illustrates a PA update procedure for a UE in a networksupporting a light connection technique according to the presentdisclosure. FIG. 6E depicts the PA update procedure in the presentdisclosure. The UE e-01 connected to the anchor eNB 6 e-02 receives anRRC connection release (RRCConnectionRelease) message from the anchoreNB 6 e-02 at step 6 e-05.

The RRC connection release message may include a Resume ID and PAinformation. The UE 6 e-01 is allocated the Resume ID and configures thePA based on the RRC connection release message.

The PA may be comprised of one or more cells. The anchor eNB 6 e-02 maytransmit to the UE 6 e-01 a list of IDs of the cells constituting the PAof the eNB or a PA identifier predetermined in the network to configurethe PA for the UE 6 e-01.

The UE 6 e-01 may check the list of the cell IDs or the cell listincluded in the paging area ID and determine on the move whether the PAhas been updated by comparing the cell ID broadcast by the eNB and thecell IDs included in the list.

If there is no data transmission/reception for the UE 6 e-01 over apredetermined time period, the anchor eNB 6 e-02 configures the UE tooperate in the light connected mode. That is, the anchor eNB 6 e-02 maytransmit an RRC connection release message including a Resume ID and PAinformation to the UE 6 e-01 such that the UE 6 e-01 enters the lightconnected mode.

If the RRC connection release message is received, the UE 6 e-01transitions to the light connected mode. The anchor eNB 6 e-01 maintainsthe UE context at step 6 e-07. The anchor eNB 6 e-01 may also maintainthe S1 bearer with the core network.

Meanwhile, the UE 6 e-01 may move close to another eNB within another PAat step 6 e-06. In this embodiment, the anchor eNB may beinterchangeably referred to as first eNB, and the other eNB may beinterchangeably referred to as second eNB.

The eNBs broadcast the cell-specific identifiers or PA identifiers oftheir own PAs using a predetermined system information block (SIB) atstep 6 e-08. As described above, the PA information may be provided insuch a way the eNB broadcasts cell IDs of the cells constituting the PAor a PA ID predetermined for use in the network.

If the system information is received, the UE 6 e-01 may determinewhether the eNB on which is has camped belongs to the same PA as the eNBwhich has transmitted the RRC connection release message(RRCConnectionRelease). If the eNBs mismatch, the UE 6 e-01 transmits anRRC connection resume message (RRCConnectionResumeRequest) to the neweNB 6 e-03 on which it has camped to update the PA at step 6 e-09.

The RRC connection resume request message may include an establishmentcause which is newly defined for use in requesting for PA update. It mayalso be possible to one of reserved bits of the legacy RRC connectionrequest message to indicate PA update request. The RRC connection resumerequest message may include at least one of Resume ID, MAC-I, andestablishment cause.

If the RCCConnectionResumeRequest message is received, the second eNB 6e-03 may identify the anchor eNB 6 e-02 which has previously served theUE 6 e-01 based on the Resume ID at step 6 e-10.

The second eNB 6 e-03 may transmit a retrieve UE context request messageto the anchor eNB 6 e-02 to request for UE context at step 6 e-11. Thesecond eNB 6 e-03 may receive a retrieve UE context response messagefrom the anchor eNB at step 6 e-12 and acquires the UE contextinformation from the retrieve UE context response message.

The second eNB 6 e-03 may perform security check using the retrieved UEcontext information. If not necessary, the UE context retrieve procedureof steps 6 e-11 and 6 e-12 may be omitted.

The second eNB 6 e-03 transmits an RRCConnectionRelease message to theUE 6 e-01 at step 6 e-13. The RRCConnectionRelease message may include anew Resume ID and PA information. As described above, the PA may becomprised of one or more cells. As described above, the anchor eNB 6e-02 may transmit to the UE 6 e-01 a list of IDs of the cellsconstituting the PA of the eNB or a PA identifier predetermined for usein the network to configure the PA for the UE 6 e-01.

The UE 6 e-01 may acquire the PA information and determine on the movewhether the PA has been updated by comparing the cell ID broadcast bythe eNB and the PA information.

After transmitting the RRCConnectionRelease message, the second eNB 6e-03 transmits a UE PA update message to the anchor eNB 6 e-02 to updatethe PA for the UE 6 e-0 at step 6 e-14. This aims to make it possiblefor the anchor eNB 6 e-02 to generate a paging message appropriately topage the UE 6 e-01 when downlink data for the UE 6 e-01 arrivesafterward.

FIG. 6F illustrates various types of PA according to the presentdisclosure.

An eNB configures a PA for a UE by transmitting the RRCConnectionReleasemessage for transiting the operation mode of the UE from the RRCconnected mode to the light connected mode as described at step 6 e-05of FIG. 6E.

If a small PA is configured for the UE as a Type 1 PA (PA1) as denotedby reference number 6 f-05, the UE is likely to report its locationfrequently because the UE should update PA whenever PA is changed as theUE moves, resulting in signaling overhead. The frequent signaling mayalso drain battery quickly. However, this facilitates for the eNB or MMEto page the UE to transmit downlink data to the UE.

In contrast, if a large PA is configured for the UE as a Type 2 PA (PA2)as denoted by reference number 6 f-10, the location registration for PAupdate is performed relatively scarcely, resulting in reduction ofbattery consumption. However, this complicates the paging procedure fordownlink data transmission to the UE in the light connected mode in viewof the eNB and MME and may cause paging signaling overhead. The presentdisclosure proposes a paging method capable of saving battery power andreducing paging signaling overhead in such a way the UE in the lightconnected mode which is disconnected from the eNB reports its mobilityin a small paging area and, after a predetermined time period elapses,in the small paging area. That is, the UE changes PA type after apredetermined time period.

Although the description is directed to the exemplary case where thechange is made in a two step-wise fashion from a small PA to a large PA,the PA change can be made in three or more step-wise fashion. That is,in the present disclosure, it may be possible to define a plurality ofPA types and to change the PA type in a step-wise fashion as timeprogresses.

In the present disclosure, it is assumed that a Type 1 PA (PA1) is a PAsmall in size (small PA), and a Type 2 PA (PA2) is a PA large in size(large PA). The type 1 PA may be comprised of one or more cells. Thetype 2 PA may be comprised of two or more cells. The type 1 or type 2 PAmay consist of a cell or a group of cells. The type 1 or 2 PA may beidentified by a list of cell identifiers or a PA identifierpredetermined for use in the network.

FIG. 6G illustrates signal flows between a UE and eNBs in a PAreconfiguration procedure according to the present disclosure.

In FIG. 6G, if data communication between the UE 6 g-01 in the RRCconnected mode and the anchor eNB 6 g-02 stops, the eNB 6 g-02 starts apredetermined timer and, if the communication is not resumed until thetimer expires, determines to release the RRC connection with the UE 6g-01.

If it is determined to release the RRC connection with the UE 6 g-01,the anchor eNB 6 g-02 transmits a control message (RRCConnectionRelease)to the UE 6 g-01 at step 6 g-05. The eNB 6 g-02 may allocates a ResumeID to the UE 6 g-01 and configure type 1 PA for mobility report in thelight connected mode using the control message. For this purpose, thecontrol message includes a Resume ID and a PA1 indicator. The type 1 PAmay be comprised of at least one cell, and the number of cellsconstituting the type 1 PA is determined by the anchor eNB 6 g-02. Theanchor eNB 6 g-02 may determine the number of cells to form the type 1PA. The PA configuration method has already been described above andthus is omitted herein.

The UE is aware of the necessity of preserving UE context based on thefact that the Resume ID is allocated. Alternatively, the anchor eNB 6g-02 may transmit a context preservation indicator for instructing theUE 6 g-01 to maintain the UE context using the control message(RRCConnectionRelease).

If the RRC connection release message including the context preservationindicator or the resume ID is received at step 6 g-05, the UE 6 g-01releases the RRC connection and may start a timer corresponding to avalid period. The UE 6 g-01 may store a valid cell list in memory andmaintain the current UE context in the memory.

The anchor eNB 6 g-02 starts a UE-specific timer (hereinafter, timer A)upon release of the connection with the UE 6 g-01. The timer A is usedfor PA type change and may be referred to as a PA change timer.

The timer A defines the mobility report time period in type 1 PA for theconnection-released UE 6 g-01, and the anchor eNB 6 g-02 may transmit apaging message to the UE 6 g-01 upon expiry of the timer A to configurea type 2 PA to the UE 6 g-01.

Accordingly, the eNB 6 g-02 transmits the RRC connection release messageto the UE 6 g-01 and then starts the timer A at step 6 g-15. The UE inthe light connected mode may performs mobility report in the type 1 PAuntil the timer A expires.

If the timer A expires at step 6 g-20, the anchor eNB 6 g-02 transmitsthe paging message to a new eNB 6 g-03 which has updated PA for themoving UE 6 g-01 at step 6 g-25. In the present disclosure, the anchoreNB 6 g-02 may be interchangeably referred to as first eNB, and the neweNB 6 g-03 may be interchangeably referred to as second eNB.

The new eNB 6 g-03 transmits the paging message to the UE 6 g-01 at step6 g-30. If the UE 6 g-01 moves but not much and thus is located in thePA of the anchor eNB 6 g-02, the anchor eNB 6 g-02 may transmit thepaging message to the UE 6 g-01 directly.

If the paging message is received, the UE 6 g-01 transmits to the neweNB 6 g-03 an RRC connection resume message including the Resume IDallocated during the RRC connection release procedure and the maintainedUE context at step 6 g-35.

If the UE in the connected mode after being disconnected from the sourceeNB 6 g-02 has moved and camped on a cell of the new eNB (second eNB) 6g-03, the new eNB 6 g-03 may receive the RRC connection resume requestmessage and identify the anchor eNB 6 g-02 as the previous serving eNBof the UE 6 g-01 based on the Resume ID included in the RRC connectionresume request message.

If the new eNB 6 g-03 receives and identifies the Resume IDsuccessfully, it can retrieve the UE context from the source eNB 6 g-02(context retrieve procedure) at step 6 g-40 and 6 g-45. The new eNB 6g-03 may receive the UE context from the source eNB 6 g-02 through a S1or X2 interface. If the new eNB 6 g-03 receives the resume ID but notidentifies the terminal, it may transmit an RRCConnectionSetup messageto trigger the legacy RRC connection establishment procedure with the UE6 g-01.

The new eNB 6 g-03 checks for the MAC-I based on the retrieved UEcontext. The MAC-I is a message authentication code computed thesecurity information (i.e., security key and security counter) of theretrieved UE context.

The new eNB 6 g-03 checks for the integrity of the message using theMAC-I of the message and the security key and security counter includedin the UE context. The new eNB 6 g-03 may generate RRC configurationinformation to be applied to the UE 6 g-01 and transmit the RRCconnection resume (RRCConnectionResume) message including theconfiguration information to the UE 6 g-01 at step 6 g-50.

The UE 6 g-01 configures the RRC connection based on the updated UEcontext and configuration information and transmits an RRC connectionresume complete message to the new eNB 6 g-03 at step 6 g-55.

The new eNB 6 g-03 configures a type 2 PA mode to the UE 6 g-01,allocates a new resume ID, and releases the connection at step 6 g-60.That is, the new eNB 6 g-03 may transmit a connection release messageincluding the new Resume ID and type 2 PA information to the UE 6 g-O atstep 6 g-60. In the procedure of FIG. 6G, the RRC Connection resumerequest message transmitted at step 6 g-35 may include a newly definedestablishment cause or have one reserved bit designated for PA updateand, in this case, steps 6 g-50 and 6 g-55 may be omitted.

FIG. 6H illustrates another procedure for PA reconfiguration for a UEaccording to the present disclosure.

In FIG. 6H if data communication between the UE 6 h-01 in the RRCconnected mode and the anchor eNB 6 h-02, the anchor eNB 6 h-02 starts apredetermined timer, and if the communication is not resumed until thetimer expires, determines to release the RRC connection with the UE 6h-01.

If it is determined to release the RRC connection with the UE 6 h-01,the anchor eNB 6 h-02 transmits a control message (RRCConnectionRelease)to the UE 6 h-01 at step 6 h-05. The eNB 6 h-02 allocates a Resume ID tothe UE 6 h-01 and configure Timer B for the UE 6 h-01 and type 1 and 2PAs for mobility report in the light connected mode using the controlmessage. For this purpose, the control message includes a Resume ID, atype 1 PA (PA1) indicator, and a type 2 PA (PA2) indicator. A PA may becomprised of at least one cell, and the number of cells for forming thePA is determined by the eNB. That is, the numbers of cells for formingthe type IPA and type 2 PA may be changed according to the configurationof the eNB. The PA configuration method has already been described aboveand thus is omitted herein.

The UE is aware of the necessity of preserving UE context based on thefact that the Resume ID is allocated. Alternatively, the anchor eNB 6h-02 may transmit a context preservation indicator for instructing theUE 6 h-01 to maintain the UE context using the control message(RRCConnectionRelease).

If the RRC connection release message including the context preservationindicator or the resume ID is received at step 6 h-05, the UE 6 h-01releases the RRC connection and may start a timer corresponding to avalid period. The UE 6 h-01 may store a valid cell list in memory andmaintain the current UE context in the memory.

The RRC connection release message may include a timer value for TimerB.

Like Timer A, Timer B is used for PA type change and may be referred toas a PA change timer.

The timer B defines the mobility report time period in type 2 PA for theUE 6 h-01, and the anchor eNB 6 h-02 and the UE 6 h-01 start the sametimer B at step 6 h-10 and 6 h-15.

If the timer B expires, the UE 6 h-01 performs mobility report in thetype 2 PA mode characterized by large PA, and the anchor eNB 6 h-02assumes that the UE 6 h-01 changes the PA for the type 2 PA.

The type 1 PA may be comprised of one or more cells. The type 2 PA maybe comprised of two or more cells. The type 1 or type 2 PA may beequivalent to one cell or a set of one or more cells. The type 1 or type2 PA may be configured in the form of a list of cell IDs or a PA IDpredetermined for use in the network. FIG. 6F depicts exemplary type 1and type 2 PAs.

In detail, the anchor eNB 6 h-02 transmits the RRCConnectionReleasemessage to the UE 6 h-01 at step 6 h-05 and starts Timer B at step 6h-15. Also, the UE 6 h-01 starts Timer B set to the timer value includedin the RRCConnectionRelease message at step 6 h-10. The start time ofthe Timer B may be included in the RRCConnectionRelease messagetransmitted to the UE 6 h-01.

The UE 6 h-01 performs mobility report in the type 1 PA mode until thetimer B expires. If the timer B expires at step 6 h-20, the UE changesthe type IPA mode to the type 2 PA mode. Since then, the UE 6 h-01performs mobility report in the type 2 PA mode.

If the UE performs mobility report in the type 2 PA mode characterizedby large PA, this means battery power conservation. The timer B of theanchor eNB 6 h-02 expires at the time when the timer B of the UE 6 h-01expires. If the timer B of the anchor eNB 6 h-02 expires at step 6 h-25,the anchor eNB 6 h-25 assumes that the UE is in the type 2 PA modewithout explicit signaling.

Meanwhile, if the UE 6 h-01 moves to another PA as at step 6 e-06 ofFIG. 6E, the UE performs the PA update procedure as described withreference to FIG. 6E.

Here, it is assumed that the UE 6 h-01 moves to another eNB (second eNBor new eNB) 6 h-03 in another PA.

The new eNB 6 h-03 may broadest its PA information in the systeminformation, and the UE 6 h-01 may determine whether the eNB on which ithas camped is identical with the eNB which has transmitted the RRCconnection release message.

If the eNBs mismatch, the UE 6 h-01 may transmit an RRC connectionresume request message to the second eNB 6 h-03 at step 6 h-40.

When the UE 6 h-01 performs the paging update procedure to be allocateda PA, there is a need of being allocated a large PA, i.e., type 2 PA.

Accordingly, it may be necessary for the UE 6 h-01 to notify the new eNB6 h-03 that the UE 6 h-1 performs the mobility report in is operating inthe type 2 PA mode. For this purpose, it may be possible to define anestablishment cause in the RRC connection resume request message beingtransmitted at step 6 h-40 or to use one of the reserved bits of the RRCconnection resume request message as a type 2 PA mode indicator(Indication 1). The RRC connection resume request message generated bythe UE 6 h-01 may include the newly defined establishment cause or thetype 2 PA mode indicator (Indication 1). In the present disclosure, thisindicator may be referred to as PA type indicator.

In the case that two PA types are defined as described above, a UE maynotify an eNB of the PA type using a 1-bit indicator.

However, the present disclosure is not limited thereby but may beinclude various modifications. For example, if two or more PA types aredefined, the UE may use multi-bit indicator rather than 1-bit indicator.

If the RRC connection resume request message is received, the new eNB 6h-03 may identify the anchor eNB 6 h-02 which has previously served theUE 6 h-01 based on the Resume ID at step 6 h-45.

Then, the second eNB 6 h-03 transmits a retrieve UE context requestmessage to the anchor eNB 6 h-02 to request for the UE context at step 6h-50. The anchor eNB 6 h-02 transmits a retrieve UE context responsemessage including the UE context to the second eNB 6 h-03 at step 6h-55.

In order to notify the new eNB 6 h-03 that the UE 6 h-01 performsmobility report in the type 2 PA mode characterized by large PA, it maybe possible to include the PA type indicator in the retrieve UE contextresponse message transmitted by the old eNB 6 h-02 at step 6 h-55instead of the RRC connection resume request message transmitted by theUE 6 h-01 at step 6 h-40.

The new eNB 6 h-03 configures a new PA mode such as type 2 PA modecharacterized by large PA to the UE 6 h-01 using the RRC connectionrelease message at step 6 h-60. Finally, the new eNB 6 h-03 reports theupdated PA mode to the anchor eNB 6 h-02 using a UE PA update message atstep 6 h-65.

FIG. 6I illustrates an autonomous PA reconfiguration procedure of a UEaccording to the present disclosure.

In FIG. 6I, if data communication between a UE in the RRC connected modeand an eNB, the eNB starts a predetermined timer, and if thecommunication is not resumed until the timer expires, transmit an RRCconnection release message to the UE to release the RRC connection withthe UE. The eNB releases the RRC connection with the UE, stores the UEcontext, and transmits the RRC connection release message according to apredetermined rule; the RRC connection release message includes a ResumeID, a timer B, and type 1 PA (PA1) and type 2 PA (PA2) information foruse by the UE to transition to the light connected mode.

The UE receives the RRC connection release message at step 6 i-01. Asdescribed above, the RRC connection release message may include at leastone of the Resume ID, Timer B, and type 1 PA and type 2 PA information.

If the RRC connection release message is received, the UE may transitionto the light connected mode at step 6 i-02.

Next, the UE starts the timer B included in the RRC connection releasemessage at step 6 i-05. The RRC connection release message may alsoinclude the information on the start time point of the timer B.

The timer B defines the mobility report time period fin type 1 PA mode,and the eNB also starts the timer B simultaneously. If the timer Bexpires, the UE performs mobility report in the type 2 PA modecharacterized by large PA, and the eNB assumes that the UE is in thetype 2 PA mode.

The UE in the light connected mode starts the timer B and determines atstep 6 i-10 whether there is data to transmit.

If there is data to transmit, the UE performs the RRC connection resumeprocedure as described with reference to FIG. 6D at step 6 i-04 so asreturns the procedure to step 6 i-01 to transmit data in the RRCconnected mode.

If there is no data to transmit, the UE determines at step 6 i-15whether the timer B has expired while performing the cell reselectionprocedure.

If the timer B has not expired, the UE determines at step 6 i-20 whetherthe suitable cell found in the cell reselection procedure belongs to thetype 1 PA. That is, the UE may determine whether it is out of the type 1PA. If the cell belongs to the type 1 PA (or if the UE is within thetype 1 PA), the UE returns procedure to step 6 i-10 to determine whetherthere is data to transmit.

If the cell does not belong to the type 1 PA, the UE performs the PAupdate procedure as described with reference to FIG. 6E to receive a newtype of PA at step 6 i-25 and updates the old type 1 PA with the newtype 1 PA at step 6 i-25.

If the timer B has expired, the UE may transition from the type 1 PAmode to the type 2 PA mode. Then, the UE may perform mobility report inthe type 2 PA mode.

If the timer B has expired, the UE determines at step 6 i-30 whether thesuitable cell found in the cell reselection procedure belongs to thetype 2 PA. That is, the UE determines whether it is out of theconfigured PA.

If the cell belongs to the type 2 PA (i.e., if the UE is within theconfigured PA), the UE returns the procedure to step 6 i-10 to determinewhether there is data to transmit.

If the cell does not belong to the type 2 PA (i.e., if the UE is out ofthe configured PA), the UE perform the PA update procedure as describedwith reference to FIG. 6E. In this case, it may be necessary to notifythe new eNB that the UE perform mobility report in the type 2 PA modecharacterized by large PA. For this purpose, it may be possible todefine an establishment cause in the RRC connection resume requestmessage being transmitted at step 6 h-40 of FIG. 6H or to use onereserved bit of the RRC connection resume request message as a type 2 PAmode indicator (Indication 1).

This indicator may be referred to as PA type indicator, and the detaileddescription thereof has been made above and thus is omitted herein.

Alternatively, it may be possible to include an indicator indicating theexpiry of the timer B of the UE and mobility report in the type 2 PAmode in the retrieve UE context response message transmitted from theold eNB to the new eNB at step 6 h-55 of FIG. 6H instead of includingthe PA type indicator in the RRC connection resume request messagetransmitted from the UE to the new eNB at step 6 h-55 of FIG. 6H(Indication 2). This indicator may also be referred to as PA typeindicator.

The UE perform the PA update procedure with this indicator to receive anew type 2 PA at step 6 i-35 and updates the old type 2 PA with the newtype 2 PA at step 6 i-30.

FIG. 6J illustrates a configuration of a UE according to an embodimentof the present disclosure.

In reference to FIG. 6J, the UE includes transceiver 6 j-05, acontroller 6 j-10, a multiplexer/demultiplexer 6 j-15, a control messageprocessor 6 j-30, higher layer processors 6 j-20 and 6 j-25, an EPSbearer manager 6 j-35, and a NAS layer entity 6 j-40. In the presentdisclosure, the controller 6 j-10 may be interchangeably referred to asa circuit, an application-specific integrated circuit, and at least oneprocessor and the controller may be coupled with the transceiver.

The transceiver 6 j-05 is identical in functionality with thetransceiver 5 m-05 of FIG. 5M and thus detailed description thereof isomitted herein. The multiplexer/demultiplexer 6 j-15 is identical infunctionality with the multiplexer/demultiplexer 5 m-15 of FIG. 5M andthus detailed description thereof is omitted herein.

The control message processor 6 j-30 is identical in functionality withthe control message processor 5 m-30 of FIG. 5M and thus detaileddescription thereof is omitted herein. The higher layer processors 6j-20 and 6 j-25 are identical in functionality with the higher layerprocessors 5 m-20 and 5 m-25 of FIG. 5M and thus detailed descriptionthereof is omitted herein.

The controller 6 j-10 checks for the scheduling command, e.g., uplinkgrants, received by the transceiver 5 m-05 and controls the transceiver6 j-05 and the multiplexer/demultiplexer 6 j-15 to perform uplinktransmission with appropriate transmission resources at an appropriatetiming.

The controller 6 j-10 may control the signaling among the functionblocks to accomplish the operations according to the proceduresdescribed with reference to the above flowcharts. In detail, thecontroller 6 j-10 may control receiving an RRC connection releasemessage. As described above, the RRC connection release message mayinclude at least one of a Resume ID, a timer B, and type 1 PA and type 2PA information. The controller 6 j-10 may control transitioning to thelight connected mode.

The controller 6 j-10 may also start a timer indicated in the RRCconnection release message. The RRC connection release message may alsoinclude the information on the start time point of the timer.

The timer defines a predetermined period for mobility report in the type1 PA mode, and the eNB also starts the same timer. If the timer expires,the controller 6 j-10 may control the UE to perform mobility report inthe type 2 PA mode characterized by large PA, and the eNB assumes thatthe UE operates in the type 2 PA mode.

The controller 6 j-10 starts the timer and performs a cell reselectionprocedure, monitoring for expiry of the timer.

If the timer expires, the controller 6 j-10 may control the UEtransitions from the type of PA mode characterized by small PA to thetype 2 PA mode characterized by large PA. Afterward, the UE may performthe mobility report in the type 2 PA mode.

If the UE moves out of the configured PA, the controller 6 j-10 controlsthe UE to perform a PA update procedure. In this situation, it may benecessary to notify the new eNB that the UE performs mobility report inthe type 2 PA mode. For this purpose, it may be possible to define anestablishment cause in the RRC connection resume request message (seestep 6 h-40 of FIG. 6H) or to use one of the reserved bits of the RRCconnection resume request message as a type 2 PA mode indicator(Indication 1).

This indicator may be referred to as PA type indicator, and detaileddescription thereof is omitted herein.

Alternatively, it may be possible to include an indicator indicating theexpiry of the timer B of the UE and mobility report in the type 2 PAmode in the retrieve UE context response message transmitted from theold eNB to the new eNB (see 6 h-55 of FIG. 6H) instead of including thePA type indicator in the RRC connection resume request messagetransmitted from the UE to the new eNB (see 6 h-55 of FIG. 6H)(Indication 2). This indicator may also be referred to as PA typeindicator.

The controller 6 j-10 controls the PA update procedure with thisindicator to receive a new type 2 PA and updates the old type 2 PA withthe new type 2 PA.

FIG. 6K illustrates a configuration of an eNB including an MME part andan S-GW part according to an embodiment of the present disclosure, andthe eNB includes transceiver 6 k-05, a controller 6 k-10 amultiplexer/demultiplexer 6 k-20, a control message processor 6 k-35,higher layer processors 6 k-25 and 6 k-30, a scheduler 6 k-15, EPSbearer entities 6 k-40 and 6 k-45, and a NAS entity 6 k-50. In thepresent disclosure, the controller 6 k-10 may be interchangeablyreferred to as a circuit, an application-specific integrated circuit,and at least one processor and the controller may be coupled with thetransceiver. The EPS bearer entities may be resided in the S-GW, and theNAS layer entity may be resided in the MME.

The transceiver 6 k-05, the multiplexer/demultiplexer 6 k-20, the higherlayer processors 6 k-25 and 6 k-30, the scheduler 6 k-15, the EPS bearerentities 6 k-40 and 6 k-45, and the NAS layer entity 6 k-50 areidentical in functionality with those described with reference to FIG.SN, detailed descriptions thereof are omitted herein.

The controller 6 k-10 may controls signaling among the function blocksto accomplish the operations in the procedures described above. Indetail, the controller 6 k-10 of the first eNB (source eNB or anchoreNB) may control the eNB to transmit an RRC connection release messageincluding a resume ID, a timer value, and an PA configurationinformation. The controller 6 k-10 may control transmitting PAconfiguration information or at least one PA type configurationinformation according to the PA update scheme of the present disclosure.

In the case of receiving a retrieve UE context request message fromanother eNB according to an embodiment of the present disclosure, thecontroller 6 k-10 may control to transmit a retrieve UE context responsemessage including a PA type indicator for use by the UE in mobilityreport.

The controller 6 k-10 of the second eNB (new eNB on which the UE hascamped) may receive an RRC connection resume request message includingthe newly defined establishment cause or the PA type indicator from theUE. Accordingly, the controller 6 k-10 may configure a PA type to the UEaccording to the PA type indicator during the PA update procedure.

Seventh Embodiment

The present disclosure proposes an operation mode transition method andapparatus for transitioning a normal terminal or a terminal operating inan extended coverage mode (hereinafter, interchangeably referred to asNB-IoT UE, Bandwidth reduced Low complexity (BL) UE, UE in CoverageEnhancement (CE), and enhanced Machine Type Communication (eMTC) UE)using a paging message in a network supporting the light connectiontechnique.

FIG. 7A illustrates architecture of an LTE system.

The detailed description of the LTE system architecture has been madealready with reference to FIG. 1A and thus is omitted herein.

FIG. 7B illustrates a protocol stack of an interface between a UE and aneNB in the LTE system.

The detailed description of the protocol stack has been made alreadywith reference to FIGS. 2B and 3B and thus is omitted herein.

FIG. 7C illustrates the concept of light connection.

The detailed description of the concept of light connection has beenmade already with reference to FIG. 6C and this omitted herein.

FIGS. 7DA and 7DB illustrate signal flows among a UE, an anchor eNB, anew eNB, and an MME for UE context and S1 bearer reuse in lightconnection procedure according to the present disclosure.

The light connection procedure of FIGS. 7DA and 7DB is identical withthat of FIGS. 6DA and 6DB and thus detailed description thereof isomitted herein.

If an RRC connection release message is received from an eNB, the UEtransitions from the RRC connected mode to the light connected mode andperforms mobility report in a PA configured for the UE in the lightconnected mode. For the UE in the light connected mode, the network hasto maintain the UE context and maintain the S1-U bearer. However, it maybe difficult for the network to maintain the UE contexts and maintainS1-U bearers for all UEs persistently. Accordingly, there is a need oftransitioning the UEs in the light connected mode to the RRC idle modeand releasing the S1-U bearers for the UEs.

FIG. 7E illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode according to the present disclosure.

In FIG. 7E, the UE 7 e-01 in the RRC connected mode is communicatingdata with the eNB 7 e-02. If the data communication stops, the eNB 7e-02 starts a predetermined time and, if data communication is notresumed before expiry of the timer, determines to release the RRCconnection of the UE 7 e-01.

The eNB 7 e-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 e-01 to release the RRCconnection. The eNB 7 e-02 allocates a Resume ID to the UE 7 e-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

If the RRC connection release message is received, the UE 7 e-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 e-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 e-05, the UE7 e-01 transitions to the light connected mode at step 7 e-10. Theanchor eNB 7 e-02 may transition the UE in the light connected mode tothe RRC idle mode. The transition from the light connected mode from theRRC idle mode may be determined by a validity period timer or triggeredby a predetermined cause. The anchor eNB 7 e-02 is an eNB whichmaintains the UE context and maintains the S1-U bearer for the UE 7e-01.

The anchor eNB 7 e-02 may determine to transition the UE 7 e-01 in thelight connected mode to the RRC idle mode at step 7 e-15. If it isdetermined to transition the UE 7 e-01 to the RRC idle mode, the anchoreNB 7 e-02 transmits a paging message to the UE 7 e-01 at step 7 e-20.Upon receipt of the paging message, the UE 7 e-01 transitions to the RRCconnected mode.

The UE 7 e-01 in the RRC connected mode transmits an RRC connectionresume request message to the anchor eNB 7 e-02 at step 7 e-25.

If the RRC connection request message is received, the anchor eNB 7 e-02identifies the RRC connection resume message for the resume ID at step 7e-30.

The anchor eNB 7 e-02 may identify the UE 7 e-01 which is supposed totransitioned to the RRC idle mode based on the Resume ID.

Accordingly, the anchor eNB 7 e-02 transmits an RRC connection releasemessage to the UE 7 e-01 to transition the UE 7 e-01 to the RRC idlemode at step 7 e-35. Upon receipt of the RRC connection release message,the UE 7 e-01 transitions to the RRC idle mode at step 7 e-40.

FIG. 7F illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode, when the UE moves to a PA ofanother eNB, according to the present disclosure.

In FIG. 7F, the UE 7 f-01 in the RRC connected mode is communicatingdata with the eNB 7 f-02. If the data communication stops, the anchoreNB 7 f-02 starts a predetermined timer and, if data communication isnot resumed before expiry of the timer, determines to release the RRCconnection of the UE 7 f-01.

The eNB 7 f-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 f-01 to release the RRCconnection. The eNB 7 f-02 allocates a Resume ID to the UE 7 f-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

If the RRC connection release message is received, the UE 7 f-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 f-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 f-05, the UE7 f-01 transitions to the light connected mode at step 7 f-10. Theanchor eNB 7 f-02 may transition the UE in the light connected mode tothe RRC idle mode. The transition from the light connected mode from theRRC idle mode may be determined by a validity period timer or triggeredby a predetermined cause. The anchor eNB 7 f-02 is an eNB whichmaintains the UE context and maintains the S1-U bearer for the UE 7f-01.

The anchor eNB 7 f-02 may determine to transition the UE 7 f-01 in thelight connected mode to the RRC idle mode at step 7 f-15. If it isdetermined to transition the UE 7 f-01 to the RRC idle mode, the anchoreNB 7 f-02 transmits a paging message to a new eNB at step 7 f-20 to theUE 7 f-01 at step 7 f-25. Upon receipt of the paging message, the UE 7f-01 transitions to the RRC connected mode.

The anchor eNB 7 f-02 may have the information on the PA for the UE 7f-01 because the UE 7 f-01 reports the PA whenever the PA is updated asthe UE 7 f-01 moves.

If the paging message is received, the UE 7 f-01 transmits an RRCconnection resume request message to the new eNB 7 f-03 at step 7 f-30.

If the RRC connection resume request message is received, the new eNB 7f-03 may identify the RRC connection resume message for the resume ID atstep 7 f-35.

Next, the second eNB 7 f-03 performs a UE context retrieval procedurewith the anchor eNB 7 f-02 at steps 7 f-40 and 7 f-45. During thisprocedure, the anchor eNB 7 f-02 may notify the new eNB 7 f-03 that theUE 7 f-01 is supposed to transition to the RRC idle mode. The new eNB 7f-03 transmits an RRC connection release message to the UE 7 f-01 atstep 7 f-50 and, upon receipt of the RRC connection release message, theUE 7 f-01 transitions to the RRC idle mode at step 7 f-55.

FIG. 7G illustrates another procedure for transitioning a UE in thelight connected mode to the RRC idle mode according to the presentdisclosure.

In reference to FIG. 7G, in a situation where the UE moves to a PA ofanother eNB, the MME makes a determination for UE's operation modetransition from the light connected mode to the RRC idle mode and, as inLTE, triggers paging of the UE instead of anchor eNB.

In FIG. 7G, the UE 7 g-01 in the RRC connected mode is communicatingdata with the anchor eNB 7 g-02. If the data communication stops, theanchor eNB 7 g-02 starts a predetermined time and, if data communicationis not resumed before expiry of the timer, determines to release the RRCconnection of the UE 7 g-01.

The eNB 7 g-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 g-01 to release the RRCconnection. The eNB 7 g-02 allocates a Resume ID to the UE 7 g-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

If the RRC connection release message is received, the UE 7 g-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 g-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 g-05, the UE7 g-01 transitions to the light connected mode at step 7 g-10. The MME 7g-04 may transition the UE in the light connected mode to the RRC idlemode. The transition from the light connected mode to the RRC idle modemay be determined by a validity period timer or triggered by apredetermined cause.

The MME 7 g-04 may determine to transition the UE 7 g-01 in the lightconnected mode to the RRC idle mode at step 7 g-15. If it is determinedto transition the UE 7 g-01 to the RRC idle mode, the MME 7 g-04transmits a paging message to the anchor eNB 7 g-02 and a new eNB 7 g-03at steps 7 g-20 and 7 g-25 and then the anchor eNB 7 g-02 and the new 7g-03 broadcast the paging message at steps 7 g-30 and 7 g-35. Uponreceipt of the paging message, the UE 7 g-01 transitions to the RRCconnected mode.

The MME 7 g-04 may have the information on the PA for the UE 7 f-01because the UE 7 g-01 reports the PA whenever the PA is updated as theUE 7 g-01 moves.

If the paging message is received, the UE 7 g-01 transmits an RRCconnection resume request message to the new eNB 7 g-03 at step 7 g-40.

If the RRC connection resume request message is received, the new eNB 7f-03 may identify the RRC connection resume message for the resume ID atstep 7 g-45.

Next, the second eNB 7 g-03 performs a UE context retrieval procedurewith the anchor eNB 7 g-02 at steps 7 g-50 and 75-55.

The paging message generated by the MME 7 g-04 may include theinformation indicating that the UE 7 g-01 is supposed to transition tothe RRC idle mode. This information may be included in the pagingmessage in the form of an indicator. This indicator may be newly definedin the paging record, or 1 bit of the paging message may be used as thisindicator. This indicator may be referred to as a UE mode transitionindicator. The UE 7 g-01 may be preconfigured so as to transition to theRRC idle mode if the paging of the UE in the light connected mode istriggered by the MME 7 g-04.

If new eNB 7 g-03 receives the paging message including the UE modetransition indicator from the MME 7 g-04, it assumes that the UE 7 g-01operates in the RRC idle mode.

The UE mode transient procedures of FIGS. 7E, 7F, and 7G fortransitioning the UE from the light connected mode to the RRC idle modemay cause signaling overhead. In order to reduce such signalingoverhead, it may be necessary to define a new indicator in the pagingmessage. This indicator indicating the transition from the lightconnected mode to the RRC idle mode may be newly defined in the pagingrecode of the paging message, or 1 bit of the paging message may bedesignated as this indicator. This indicator may be referred to as a UEmode transition indicator. This indicator may be identical with ordifferent from the indicator transmitted from the MME to the eNBs.

FIG. 7H illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode using a paging message including anRRC idle mode transition indicator.

In FIG. 7H, the UE 7 h-01 in the RRC connected mode is communicatingdata with the anchor eNB 7 h-02. If the data communication stops, theeNB 7 h-02 starts a predetermined time and, if data communication is notresumed before expiry of the timer, determines to release the RRCconnection of the UE 7 h-01.

The eNB 7 h-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 h-01 to release the RRCconnection. The eNB 7 h-02 allocates a Resume ID to the UE 7 h-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

If the RRC connection release message is received, the UE 7 h-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 h-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 h-05, the UE7 h-01 transitions to the light connected mode at step 7 h-10. Theanchor eNB 7 h-02 may transition the UE in the light connected mode tothe RRC idle mode. The transition from the light connected mode from theRRC idle mode may be determined by a validity period timer or triggeredby a predetermined cause. The anchor eNB 7 h-02 is an eNB whichmaintains the UE context and maintains the S1-U bearer for the UE 7h-01.

The anchor eNB 7 h-02 may determine to transition the UE 7 h-01 in thelight connected mode to the RRC idle mode at step 7 h-15.

If it is determined to transition the UE 7 h-01 to the RRC idle mode,the anchor eNB 7 h-02 is capable of transmitting a paging messageincluding an indicator indicating mode transition to the RRC idle modeto the UE 7 h-01. Accordingly, the anchor eNB 7 h-02 transmits a pagingmessage including the mode transition indicator to the UE 7 h-02 at step7 h-20.

Upon receipt of the paging message, the UE 7 h-01 checks the pagingmessage for the mode transition indicator and transitions to the RRCidle mode directly at step 7 h-25.

The mode transition indicator included in the paging message is theinformation instructing the UE to transition to the RRC idle modedirectly. This indicator may be newly defined in the paging record ofthe paging message, or 1 bit of the paging message may be used as thisindicator. This indicator may be referred to as a UE mode transitionindicator.

After transitioning to the RRC idle mode, the UE 7 h-01 transmits to theanchor eNB 7 h-02 an RRC connection resume request message to notify theanchor eNB 7 h-02 that the UE has successfully transitioned to the RRCidle mode at step 7 h-30.

If the RRC connection resume request message is received, the anchor eNB7 h-02 checks the RRC connection resume request message for the resumeID to recognize that the UE 7 h-01 has successfully transitioned to theRRC idle mode. The anchor eNB 7 h-02 may start a predetermined timerafter transmitting the paging message and, if an RRC connection resumerequest message is not received before expiry of the timer, determinethat the paging message is lost 7 h-35.

FIG. 7I illustrates a method for an eNB to transition a UE in the lightconnected mode to the RRC idle mode using a paging message including anRRC idle mode transition indicator, when the UE moves to a PA of anothereNB, according to the present disclosure.

In FIG. 7I, the UE 7 i-01 in the RRC connected mode is communicatingdata with the eNB 7 i-02. If the data communication stops, the anchoreNB 7 i-02 starts a predetermined timer and, if data communication isnot resumed before expiry of the timer, determines to release the RRCconnection of the UE 7 i-01.

The eNB 7 i-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 i-01 to release the RRCconnection. The eNB 7 i-02 allocates a Resume ID to the UE 7 i-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

[If the RRC connection release message is received, the UE 7 i-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 i-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 i-05, the UE7 i-01 transitions to the light connected mode at step 7 i-10. Theanchor eNB 7 i-02 may transition the UE in the light connected mode tothe RRC idle mode. The transition from the light connected mode from theRRC idle mode may be determined by a validity period timer or triggeredby a predetermined cause. The anchor eNB 7 i-02 is an eNB whichmaintains the UE context and maintains the S1-U bearer for the UE 7i-01.

The anchor eNB 7 f-02 may determine to transition the UE 7 i-01 in thelight connected mode to the RRC idle mode at step 7 i-15. If it isdetermined to transition the UE 7 i-01 to the RRC idle mode, the anchoreNB 7 i-02 is capable of transmitting a paging message including anindicator indicating mode transition to the RRC idle mode. The anchoreNB 7 i-02 transmits a paging message including the mode transitionindicator to a new a new eNB 7 i-03 at step 7 i-20, and the new eNBbroadcasts the paging message to the UE 7 i-01 at step 7 i-25.

Upon receipt of the paging message, the UE 7 i-01 checks the pagingmessage for the mode transition indicator and transitions to the RRCidle mode immediately at step 7 i-30.

The mode transition indicator included in the paging message is theinformation instructing the UE to transition to the RRC idle modedirectly. This indicator may be newly defined in the paging record ofthe paging message, or 1 bit of the paging message may be used as thisindicator. This indicator may be referred to as a UE mode transitionindicator.

After transitioning to the RRC idle mode, the UE 7 i-01 transmits to theanchor eNB 7 i-02 an RRC connection resume request message to notify thenew eNB 7 i-03 that the UE has successfully transitioned to the RRC idlemode at step 7 i-40.

If the RRC connection resume request message is received, the new eNB 7i-03 may check the RRC connection resume message for the resume ID andrecognize that the UE 7 h-01 has successfully transitioned to the RRCidle mode at step 7 i-35. The new eNB 7 h-03 may start a predeterminedtimer after broadcasting the paging message and, if an RRC connectionresume request message is not received before expiry of the timer,determine that the paging message is lost 7 i-40. FIG. 7J is a signalflow diagram illustrating another procedure for transitioning a UE inthe light connected mode to the RRC idle mode according to the presentdisclosure.

In reference to FIG. 7J, in a situation where the UE moves to a PA ofanother eNB, the MME makes a determination for UE's operation modetransition from the light connected mode to the RRC idle mode and, as inLTE, triggers paging of the UE instead of anchor eNB; the paging messagegenerated by the MME includes an indicator indicating transition of theUE in the light connected mode to the RRC idle mode.

In FIG. 7G, the UE 7 j-01 in the RRC connected mode is communicatingdata with the anchor eNB 7 j-02. If the data communication stops, theanchor eNB 7 j-02 starts a predetermined time and, if data communicationis not resumed before expiry of the timer, determines to release the RRCconnection of the UE 7 j-01.

The eNB 7 j-02 may maintain the UE context and transmit an RRCconnection release message to instruct the UE 7 j-01 to release the RRCconnection. The eNB 7 j-02 allocates a Resume ID to the UE 7 j-01 andconfigures a PA for mobility report in the light connected mode usingthe RRC connection release message. That is, the RRC connection releasemessage may include the resume ID and PA information. The PAconfiguration method has been described above and thus detaileddescription thereof is omitted herein.

If the RRC connection release message is received, the UE 7 j-01transitions to the light connected mode (or inactive mode) and is awarethat it has to maintain the UE context based on the fact that the resumeID is allocated or on an explicit context preservation indicatorincluded in the RRC connection release message. The RRC connectionrelease message may include a list of cells for use of the maintained UEcontext in RRC connection reconfiguration during the contextpreservation period of the eNB or the context validity period of the UE.The eNB 7 g-02 maintains the UE context and maintains the S1 bearer forthe UE after the RRC connection is released.

If the RRC connection release message is received at step 7 j-05, the UE7 j-01 transitions to the light connected mode at step 7 j-10. The MME 7j-04 may transition the UE in the light connected mode to the RRC idlemode. The transition from the light connected mode to the RRC idle modemay be determined by a validity period timer or triggered by apredetermined cause.

The MME 7 j-04 may determine to transition the UE 7 j-01 in the lightconnected mode to the RRC idle mode at step 7 j-15. If it is determinedto transition the UE 7 j-01 to the RRC idle mode, the MME 7 j-04transmits a paging message including a mode transition indicatorindicating transition to the RRC idle mode to the anchor eNB 7 j-02 anda new eNB 7 j-03 at steps 7 j-20 and 7 j-25. Next, the anchor eNB 7 j-02and the new 7 j-03 broadcast the paging message at steps 7 j-30 and 7j-35.

The MME 7 j-04 may have the information on the PA for the UE 7 j-01because the UE 7 j-01 reports the PA whenever the PA is updated as theUE 7 j-01 moves.

If the paging message is received, the UE 7 j-01 checks the pagingmessage for the mode transition indicator and transitions to the RRCidle mode immediately at step 7 j-40.

The mode transition indicator included in the paging message is theinformation instructing the UE to transition to the RRC idle modedirectly. This indicator may be newly defined in the paging record ofthe paging message, or 1 bit of the paging message may be used as thisindicator.

After transitioning to the RRC idle mode, the UE 7 j-01 transmits an RRCconnection resume request message to the new eNB 7 j-03 to inform thatthe UE 7 j-01 has successfully transitioned to the RRC idle mode at step7 j-45. The new eNB 7 j-03 may start a predetermined timer afterbroadcasting the paging message and, if an RRC connection resume requestmessage is not received before expiry of the timer, determine that thepaging message is lost 7 i-50. FIG. 7K is III a flowchart illustrating aUE operation, when a paging message is received, according to thepresent disclosure. In FIG. 7K, the UE in the RRC connected mode iscommunicating data with an eNB at step 7 k-01.

If the data communication stops and does not resume before apredetermined time period elapses, the UE may receive an RRC connectionrelease message at step 7 k-02. The RRC connection release message mayinclude at least one of a resume ID and PA information.

Next, the UE transitions to the light connected mode at step 7 k-03. TheUE stores the resume ID and UE context and, if a PA mode is configured,transitions to the light connected mode. The UE may report mobility tothe network, when it moves along the configured PA area.

Afterward, the UE may receive a paging message at step 7 k-04.

If the paging message is received, the UE determines at step 7 k-10whether the paging message include a mode transition indicatorindicating transition to the RRC idle mode.

The mode transition indicator included in the paging message is theinformation instructing the UE to transition to the RRC idle modedirectly. This indicator may be newly defined in the paging record ofthe paging message, or 1 bit of the paging message may be used as thisindicator. In the present disclosure, this indicator may be referred toas a UE mode transition indicator.

If it is determined that the paging message includes no mode transitionindicator, the UE triggers an RRC connection resume procedure at step 7k-15 to return the procedure to step 7 k-01.

In the case that the eNB or the MME has transmitted the paging messageincluding the mode transition indicator indicating transition to theidle mode, the UE may transition to the idle mode upon receipt of theRRC connection release message. In the case that the MME triggers pagingof the UE, the MME may transmit the paging message including the UE modetransition indicator to the eNBs. If the MME triggers paging of the UE,it generates the paging message including the UE mode transitionindicator.

If it is determined that the paging message includes the mode transitionindicator, the UE transitions to the RRC idle mode immediately at step 7k-20. After transitioning to the RRC idle mode, the UE transmits an RRCconnection resume request message to notify the eNB that the UE hassuccessfully transitioned to the RRC idle mode at step 7 k-25.

FIG. 7L illustrates a configuration of a UE according to an embodimentof the present disclosure.

In reference to FIG. 7L, the UE includes transceiver 7 l-05, acontroller 7 l-10, a multiplexer/demultiplexer 7 l-15, a control messageprocessor 7 l-30, higher layer processors 7 l-20 and 7 l-25, an EPSbearer manager 7 l-35, and a NAS layer entity 7 l-40. In the presentdisclosure, the controller 7 l-10 may be interchangeably referred to asa circuit, an application-specific integrated circuit, and at least oneprocessor and the controller may be coupled with the transceiver.

The transceiver 7 l-05, multiplexer/demultiplexer 7 l-15, controlmessage processor 7 l-30, and higher layer processors 7 l-20 and 7 l-25are identical in functionality with the those of FIG. 5M and thusdetailed descriptions thereof are omitted herein.

The controller 7 l-10 checks for the scheduling command, e.g., uplinkgrants, received by the transceiver 7 l-05 and controls the transceiver7 l-05 and the multiplexer/demultiplexer 7 l-15 to perform uplinktransmission with appropriate transmission resources at an appropriatetiming.

The controller 7 l-10 may control the signaling among the functionblocks to accomplish the operations according to the proceduresdescribed with reference to the above flowcharts. In detail, thecontroller 7 l-10 may control the UE in the RRC connected UE tocommunicate data with an eNB.

The controller 7 l-10 may start a timer, when the data communicationsteps, and control the UE to receive an RRC connection release messageif the data communication does not resume before expiry of the timer.The controller 7 l-10 may control the UE to transition to the lightconnected mode. The controller 7 l-10 may control the UE to receive thepaging message.

If the paging message is received, the controller 7 l-10 may check theaging message for the mode transition indicator indicating transition tothe RRC idle mode.

The mode transition indicator included in the paging message is theinformation instructing the UE to transition to the RRC idle modedirectly. This indicator may be newly defined in the paging record ofthe paging message, or 1 bit of the paging message may be used as thisindicator. In the present disclosure, this indicator may be referred toas a UE mode transition indicator.

If it is determined that the paging message includes no mode transitionindicator, the controller 7 l-10 triggers an RRC connection resumeprocedure transition the UE back to the RRC connected mode.

In the case that the eNB or the MME has transmitted the paging messageincluding the mode transition indicator indicating transition to theidle mode, the UE may transition to the idle mode upon receipt of theRRC connection release message.

If it is determined that the paging message includes the mode transitionindicator, the controller 7 l-10 controls the UE to transition to theRRC idle mode immediately. After transitioning the UE to the RRC idlemode, the controller 7 l-10 controls UE to transmit an RRC connectionresume request message to notify the eNB that the UE has successfullytransitioned to the RRC idle mode.

FIG. 7M illustrates a configuration of an eNB including an MME part andan S-GW part according to an embodiment of the present disclosure, andthe eNB includes transceiver 7 m-05, a controller 7 m-10 amultiplexer/demultiplexer 7 m-20, a control message processor 7 m-35,higher layer processors 7 m-25 and 7 m-30, a scheduler 7 m-15, EPSbearer entities 7 m-40 and 7 m-45, and a NAS entity 7 m-50. In thepresent disclosure, the controller 7 m-10 may be interchangeablyreferred to as a circuit, an application-specific integrated circuit,and at least one processor and the controller may be coupled with thetransceiver. The EPS bearer entities may be resided in the S-GW, and theNAS layer entity may be resided in the MME.

The transceiver 7 m-05, the multiplexer/demultiplexer 7 m-20, the higherlayer processors 7 m-25 and 7 m-30, the scheduler 7 m-15, the EPS bearerentities 7 m-40 and 7 m-45, and the NAS layer entity 7 m-50 areidentical in functionality with those described with reference to FIG.5N, detailed descriptions thereof are omitted herein.

The controller 7 m-10 may controls signaling among the function blocksto accomplish the operations in the procedures described above. Indetail, the controller 7 m-10 may determine whether to transition the UEto the idle mode and transmits, if the mode transition determination ismade, a paging message to transition the UE to the RRC connected modeand then transmits an RRC connection release message to transition theUE to the RRC idle mode.

The controller 7 m-10 may include the UE mode transition indicator inthe paging message to transition the UE to the idle mode.

If a paging message is received from the eNB, the controller 7-10 maydetermine whether to transition to the UE to the idle mode based on themode transition indicator included in the paging message or according toa predetermined rule. In order to transition the UE to the idle mode,the controller 7 m-10 may control the eNB to transmit a paging messageto transition the UE to the RRC connected mode and then an RRCconnection release message to transition the UE to the RRC idle mode ormay control the eNB to transmit the paging message including the UE modeswitching indicator.

As described above, the access control method of the present disclosureis advantageous in terms of reducing UE operation complexity by applyinga single access control procedure

Also, the access control method of the present disclosure isadvantageous in that the eNB can configure the DRX operation of a UEefficiently by changing the DRX cycle dynamically.

Also, the access control method of the present disclosure isadvantageous in terms of adjusting network overload by specifying theoperation of paging within multiple areas of a cell in a heterogonousenvironment including eNBs with different cell sizes.

Also, the access control method of the present disclosure isadvantageous in terms of increasing successful reception probability andreducing latency in data transmission.

Also, the access control method of the present disclosure isadvantageous in terms of protecting against data transmissioninterruption phenomenon and improving data communication efficiency byadopting a data interruption time reduction mechanism and specifying UEoperation for failure of data interruption time reduction.

Also, the access control method of the present disclosure isadvantageous in terms of saving battery power and reducing signalingoverhead by transitioning the operation mode of the UE disconnected fromthe network supporting the light connection to a large paging areapreference mode autonomously.

Also, the access control method of the present disclosure isadvantageous in terms of reducing signaling overhead between the UE andthe network by transitioning the UE in the light connected mode to theidle mode based on the paging message from the eNB.

The methods specified in claims and specification can be implemented byhardware, software, or a combination of them.

In the case of being implemented in software, it may be possible tostore at least one program (software module) in a computer-readablestorage medium. The at least one program stored in the computer-readablestorage medium may be configured for execution by at least one processorembedded in an electronic device. The at least one program includesinstructions executable by the electronic device to perform the methodsdisclosed in the claims and specifications of the present disclosure.

Such a program (software module or software program) may be stored in anon-volatile memory such as random access memory (RAM) and flash memory,Read Only Memory (ROM), Electrically Erasable Programmable Read OnlyMemory (EEPROM), a magnetic disc storage device, a Compact Disc-ROM(CD-ROM), Digital Versatile Discs (DVDs) or other type of opticalstorage device, and a magnetic cassette. It may also be possible tostore the program in a memory device implemented in combination of partor whole of the aforementioned media. The memory may include a pluralityof memories.

The program may be stored in an attachable storage device accessiblethrough a communication network implemented as a combination ofInternet, intranet, Local Area Network (LAN), Wireless LAN (WLAN), andStorage Area Network (SAN). The storage device may be attached to thedevice performing the methods according to embodiments of the presentdisclosure by means of an external port. It may also be possible for aseparate storage device installed on a communication network to attachto the device performing the methods according to embodiments of thepresent disclosure.

It is to be appreciated that those skilled in the art can change ormodify the embodiments without departing the technical concept of thisdisclosure. Accordingly, it should be understood that above-describedembodiments are essentially for illustrative purpose only but not in anyway for restriction thereto. Thus, the scope of the disclosure should bedetermined by the appended claims and their legal equivalents ratherthan the specification, and various alterations and modifications withinthe definition and scope of the claims are included in the claims.

In the above described embodiments of the present disclosure, theoperations are selectively performed or omitted. In each embodiment ofthe present disclosure, the operations are not necessary to be performedin the sequential order as depicted but may be performed in a changedorder.

Some or all of the disclosures described below are provided to helpunderstand the present disclosure. Accordingly, the detaileddescriptions of the disclosures are to express part of the method andapparatus proposed in the present disclosure. That is, it is preferredto approach the content of the specification semantically rather thansyntactically.

Although various embodiments of the present disclosure have beendescribed using specific terms, the specification and drawings are to beregarded in an illustrative rather than a restrictive sense in order tohelp understand the present disclosure. It is obvious to those skilledin the art that various modifications and changes can be made theretowithout departing from the broader spirit and scope of the disclosure.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a user equipment (UE) in acommunication system, the method comprising: transmitting, to a sourcebase station, UE capability information including information indicatingwhether the UE supports a handover without random access; receiving,from the source base station, a radio resource control (RRC) message forhandover, the RRC message including information indicating whether arandom access procedure for a target base station is skipped;identifying whether the RRC message includes uplink resourceinformation; and in case that the RRC message does not include theuplink resource information: monitoring a physical downlink controlchannel (PDCCH) of the target base station, and transmitting a completemessage for the handover based on uplink resource information includedin control information upon receiving the control information on thePDCCH of the target base station.
 2. The method of claim 1, whereintransmitting the UE capability information comprises receiving, from thesource base station, a UE capability enquiry message before transmittingthe UE capability information.
 3. The method of claim 1, whereinmonitoring the PDCCH comprises: starting a timer set to a timer valueincluded in the RRC message; and performing, in case that no controlinformation is received on the PDCCH before expiry of the timer, cellselection for determining a suitable cell and performing a random accessprocedure to the suitable cell.
 4. The method of claim 3, wherein thetimer value is less than another timer value configured to the UE fordetermining handover failure.
 5. The method of claim 1, whereinidentifying whether the RRC message includes the uplink resourceinformation further comprises: in case that the RRC message includes theuplink resource information, transmitting the complete message for thehandover based on the uplink resource information included in the RRCmessage.
 6. A method performed by a source base station in acommunication system, the method comprising: receiving, from a userequipment (UE), UE capability information including informationindicating whether the UE supports a handover without random access;transmitting, to a target base station, a handover request message;receiving, from the target base station, a handover requestacknowledgement (ACK) message as a response to the handover requestmessage; in case that the handover request ACK message includes uplinkresource information, transmitting, to the UE, a radio resource control(RRC) message including the uplink resource information; and in casethat the handover request ACK message does not include the uplinkresource information, transmitting, to the UE, the RRC message withoutthe uplink resource information, wherein the RRC message includesinformation indicating whether a random access procedure for the targetbase station is skipped.
 7. The method of claim 6, wherein receiving theUE capability information comprises transmitting, to the UE, a UEcapability enquiry message before receiving the UE capabilityinformation.
 8. The method of claim 6, wherein the handover request ACKmessage and the RRC message include a timer value, and wherein the timervalue is less than another timer value configured to the UE fordetermining handover failure.
 9. A user equipment (UE) in acommunication system, the UE comprising: a transceiver; and a controllercoupled with the transceiver and configured to: transmit, to a sourcebase station, UE capability information including information indicatingwhether the UE supports a handover without random access, receive, fromthe source base station, a radio resource control (RRC) message forhandover, the RRC message including information indicating whether arandom access procedure for a target base station is skipped, identifywhether the RRC message includes uplink resource information, and incase that the RRC message does not include the uplink resourceinformation: monitor a physical downlink control channel (PDCCH) of thetarget base station, and transmit a complete message for the handoverbased on uplink resource information included in control informationupon receiving the control information on the PDCCH of the target basestation.
 10. The UE of claim 9, wherein the controller is furtherconfigured to: receive, from the source base station, a UE capabilityenquiry message before transmitting the UE capability information. 11.The UE of claim 9, wherein the controller is further configured to:start a timer set to a timer value included in the RRC message, andperform, in case that no control information is received on the PDCCHbefore expiry of the timer, cell selection for determining a suitablecell and perform a random access procedure to the suitable cell.
 12. TheUE of claim 11, wherein the timer value is less than another timer valueconfigured to the UE for determining handover failure.
 13. The UE ofclaim 9, wherein the controller is further configured to, in case thatthe RRC message includes the uplink resource information, transmit thecomplete message for the handover based on the uplink resourceinformation included in the RRC message.
 14. A source base station in awireless communication system, the source base station comprising: atransceiver; and a controller coupled with the transceiver andconfigured to: receive, from a user equipment (UE), UE capabilityinformation including information indicating whether the UE supports ahandover without random access, transmit, to a target base station, ahandover request message, receive, from the target base station, ahandover request acknowledgement (ACK) message as a response to thehandover request message, in case that the handover request ACK messageincludes uplink resource information, transmit, to the UE, a radioresource control (RRC) message including the uplink resourceinformation, and in case that the handover request ACK message does notinclude the uplink resource information, transmit, to the UE, the RRCmessage without the uplink resource information, wherein the RRC messageincludes information indicating whether a random access procedure forthe target base station is skipped.
 15. The source base station of claim14, wherein the controller is configured to transmit, to the UE, a UEcapability enquiry message before receiving the UE capabilityinformation.
 16. The source base station of claim 14, wherein thehandover request ACK message and the RRC message include a timer value,and wherein the timer value is less than another timer value configuredto the UE for determining handover failure.